The provided texts offer a comprehensive exploration of object-oriented programming (OOP) in JavaScript, starting with fundamental concepts like objects, object literals, factory functions, and constructor functions, contrasting them with procedural programming. The material progresses to cover prototypal inheritance, explaining the prototype chain, constructor properties, and the significance of shared methods for memory efficiency and code reuse. Advanced topics such as property descriptors, abstraction, and the use of Getters and Setters are discussed to illustrate how to manage object behavior and encapsulate data. The explanation extends to modern JavaScript features including ES6 classes as syntactic sugar over prototypes, hoisting behavior, and the creation of static methods and private members. Furthermore, the texts introduce modules (CommonJS and ES6) for organizing and reusing code, along with the role of npm for package management and third-party libraries. Finally, the sources touch upon asynchronous JavaScript, covering callbacks, Promises, and async/await for handling non-blocking operations.

Node.js and JavaScript Fundamentals Study Guide

Quiz

Explain the primary purpose of both Node.js and Visual Studio Code as introduced in the source material. Why are both recommended for the course?
Describe the process of creating a new JavaScript file and running it using Node.js within the Visual Studio Code environment. Include the specific commands or shortcuts mentioned.
What are the key components of the Visual Studio Code interface, as highlighted in the text? Briefly explain the function of the activity bar and the status bar.
Explain the difference between primitive and object data types in JavaScript, focusing on how they are passed (by value vs. by reference) and the implications of this difference.
Define what it means for objects in JavaScript to be dynamic. Provide an example of how you can dynamically add, modify, and delete properties from an existing object.
What is a JavaScript closure? Explain how closures enable the creation of private variables and methods within constructor functions.
Describe the purpose and basic syntax of Getters and Setters in JavaScript. How do they contribute to encapsulation within object-oriented programming?
Explain the concept of the prototype chain in JavaScript. How does it enable objects to inherit properties and methods from other objects?
What is the significance of the this keyword in JavaScript, and how does its behavior differ when a method is detached from its object context? How does strict mode affect this?
Briefly explain the concept of abstraction in object-oriented programming and describe at least two ways to achieve private properties or methods in JavaScript classes as discussed in the source material.

Quiz Answer Key

Node.js is a runtime environment that allows JavaScript code to be executed outside of a web browser, primarily used for backend development. Visual Studio Code (VS Code) is an Integrated Development Environment (IDE) used for writing and debugging code. Both are recommended for the course to provide an environment for writing and executing JavaScript code for backend applications.
To create a new JavaScript file in VS Code, open the project folder and click the new file icon or use the keyboard shortcut (Ctrl+N or Cmd+N). Name the file with a .js extension (e.g., code.js). To run it with Node.js, open the integrated terminal in VS Code (Ctrl+` or Cmd+`) and use the command node filename.js (e.g., node code.js).
Key components of VS Code include the activity bar (on the left with icons for Explorer, Search, Source Control, Run and Debug, and Extensions) and the status bar (at the bottom showing errors/warnings, line number, and language). The activity bar allows navigation between project files, search, version control, debugging, and extensions. The status bar provides contextual information about the current file and project.
Primitive data types (number, string, boolean, etc.) are passed by value, meaning a copy of the value is assigned to a new variable, and changes to one do not affect the other. Object data types (including objects, arrays, and functions) are passed by reference, meaning both variables point to the same object in memory, so changes to one are reflected in the other.
Objects in JavaScript are dynamic because you can add, modify, and delete their properties and methods after they have been created. For example, if you have const person = { name: ‘Alice’ };, you can add a property with person.age = 30;, modify it with person.name = ‘Bob’;, and delete it with delete person.age;.
A JavaScript closure is an inner function that has access to variables in its outer (enclosing) function’s scope, even after the outer function has finished executing. Closures enable the creation of private variables by defining variables within the outer function’s scope, which are then only accessible by the inner function’s methods, effectively hiding them from the outside.
Getters are methods that allow you to retrieve the value of an object’s property, while Setters allow you to modify the value of a property. They are defined within an object literal or class using the get and set keywords followed by the property name and a function. They contribute to encapsulation by providing controlled access to an object’s internal properties, allowing for validation or other logic during property access or modification.
The prototype chain in JavaScript is a mechanism of inheritance where objects can inherit properties and methods from other objects. Every object (except the root object) has an internal link to another object called its prototype. When you try to access a property of an object, JavaScript first looks at the object itself. If the property is not found, it then looks at the object’s prototype, and so on, up the chain until the property is found or the end of the chain is reached.
The this keyword in JavaScript refers to the object that is currently executing the code. Its behavior depends on how a function is called. When a method is detached from its object (e.g., assigned to a variable and called independently), this typically loses its binding to the original object and may refer to the global object (in non-strict mode in browsers) or be undefined (in strict mode). Strict mode enforces more consistent behavior and helps prevent unintended global variable modifications.
Abstraction in OOP involves hiding complex implementation details and exposing only the essential information to the user. Two ways to achieve private properties or methods in JavaScript classes discussed are using ES6 Symbols (which create unique, less accessible identifiers, though not truly private) and using ES2022 private class fields and methods denoted by a hash (#) prefix, which provides truly private encapsulation not accessible from outside the class.

Essay Format Questions

Discuss the significance of modularity in JavaScript development, particularly within the Node.js environment. Explain how CommonJS and ES6 modules facilitate encapsulation and code organization, highlighting their key differences and use cases based on the source material.
Analyze the concept of asynchronous programming in JavaScript. Compare and contrast the use of callbacks, promises, and async/await for managing asynchronous operations, discussing the benefits and drawbacks of each approach as presented in the provided excerpts.
Explain the principles of object-oriented programming (OOP) as introduced in the source material. Discuss how JavaScript supports these principles through features like constructor functions, prototypes, classes, and encapsulation techniques such as closures and Getters/Setters.
Describe the role and importance of package management in Node.js using npm. Discuss how package.json and semantic versioning contribute to dependency management, project stability, and collaboration among developers, referencing the concepts of global vs. local package installations.
Discuss the concept of privacy and data encapsulation in JavaScript. Analyze the different techniques for achieving privacy, such as naming conventions, closures, Symbols, weak maps, and private class fields (#), evaluating their effectiveness and use cases based on the information provided in the source material.

Glossary of Key Terms

Node.js: A runtime environment that allows JavaScript code to be executed outside of a web browser, primarily used for server-side development.
Visual Studio Code (VS Code): A free source code editor made by Microsoft for Windows, Linux, and macOS, used for writing and debugging code.
IDE (Integrated Development Environment): A software application that provides comprehensive facilities to computer programmers for software development.
JavaScript: A high-level, often just-in-time compiled, and multi-paradigm programming language that conforms to the ECMAScript specification.
Console: A window in which text-based output from and input to a computer program takes place. In web development and Node.js, often used for logging information.
File Explorer (Windows): A file manager application used by Windows operating systems for browsing and managing files and folders.
Finder (macOS): The default file manager and the graphical user interface shell used in all Macintosh operating systems.
Project: A collection of related files and folders that constitute a software development effort.
File Extension: A suffix at the end of a filename indicating the type of file. For JavaScript files, it is .js.
console.log(): A JavaScript function used to print output to the console.
Integrated Terminal: A terminal emulator directly within an IDE like VS Code, allowing developers to run command-line tools without switching applications.
Activity Bar (VS Code): The vertical bar on the left side of the VS Code window that allows switching between different views like Explorer, Search, etc.
Status Bar (VS Code): The horizontal bar at the bottom of the VS Code window that displays information about the current project and file.
Primitive Data Types: Basic data types in JavaScript that are passed by value, including number, string, boolean, big int, undefined, null, and symbol.
Object Data Type: A complex data type in JavaScript that can hold collections of key-value pairs. Includes objects, arrays, and functions, and is passed by reference.
Pass by Value: When a variable holding a primitive value is assigned to another variable, a copy of the value is created in a new memory location.
Pass by Reference: When a variable holding a reference to an object is assigned to another variable, both variables point to the same object in memory.
Dynamic Objects: Objects in JavaScript that can have their properties and methods added, modified, or deleted after creation.
Constructor Function: A function in JavaScript that is used with the new keyword to create and initialize objects.
Instantiation: The process of creating a new instance of an object from a class or constructor function.
Closure: An inner function in JavaScript that has access to the outer (enclosing) function’s variables—scope chain—even after the outer function has finished executing.
Encapsulation: The bundling of data (properties) and methods that operate on the data into a single unit (object), and restricting direct access to some of the object’s components.
Getter: A special method that is used to get the value of an object’s property.
Setter: A special method that is used to set the value of an object’s property.
Object Literal: A way to create objects in JavaScript using curly braces {} and defining properties as key-value pairs.
Prototype: An object that serves as a template for other objects. Objects inherit properties and methods from their prototype.
Prototype Chain: A sequence of objects linked together via their prototypes, used for inheritance and looking up properties and methods.
this Keyword: A keyword in JavaScript that refers to the object that is currently executing the code. Its value depends on how the function is called.
Strict Mode: A feature in JavaScript that enforces stricter parsing and error handling on your code, helping to avoid common pitfalls and unsafe practices.
Abstraction (OOP): Hiding complex implementation details and showing only essential information to the user.
ES6 (ECMAScript 2015): A major update to the JavaScript language standard that introduced new features like classes, modules, arrow functions, etc.
Symbol (ES6): A primitive data type whose instances are unique and immutable, often used to create private object properties.
Weak Map (ES6): A collection of key-value pairs in which keys must be objects, and unlike Maps, WeakMap keys are not strongly referenced, allowing them to be garbage collected if they are not referenced elsewhere.
Private Class Fields (ES2022): Class fields declared with a # prefix that are truly private and not accessible from outside the class.
Module: A self-contained unit of code that can be imported and used in other parts of a program. In Node.js, each file is treated as a separate module.
CommonJS: A module system for JavaScript, primarily used in Node.js, that uses require() to import modules and module.exports to export them.
ES6 Modules: A standardized module system for JavaScript that uses import to import modules and export to export them, supported in modern browsers and Node.js.
require(): A function in CommonJS used to import modules.
module.exports: An object in CommonJS used to define what a module exports.
import (ES6): A keyword in ES6 used to import modules.
export (ES6): A keyword in ES6 used to export modules.
package.json: A file at the root of a Node.js project that describes the project, its dependencies, scripts, and other metadata.
npm (Node Package Manager): The default package manager for Node.js. It is the world’s largest software registry, containing over a million packages.
Dependency: A library or package that a project relies on to function correctly.
npm install: A command used to download and install the dependencies listed in a project’s package.json file.
Semantic Versioning (SemVer): A versioning standard using a three-part number (MAJOR.MINOR.PATCH) to indicate the nature of changes in a software release.
Global Packages (npm): Packages installed in a system-wide directory, making them accessible from any project. Installed using the -g or –global flag.
Local Packages (npm): Packages installed within a specific project’s node_modules directory, only available to that project.
npm publish: A command used to upload a package to the npm registry.
Asynchronous Programming: A programming paradigm that allows multiple tasks to run concurrently without blocking the main execution thread.
Synchronous Programming: A programming paradigm where tasks are executed sequentially, and each task must complete before the next one can start.
Callback Function: A function passed as an argument to another function, to be executed at a later point, often after an asynchronous operation completes.
Callback Hell (Pyramid of Doom): A situation in asynchronous JavaScript code where multiple nested callbacks make the code difficult to read and maintain.
Promise: An object representing the eventual completion (either success or failure) of an asynchronous operation and its resulting value.
then(): A method of a Promise that is called when the promise is fulfilled (resolved).
catch(): A method of a Promise that is called when the promise is rejected.
async: A keyword used to define an asynchronous function, which implicitly returns a Promise.
await: A keyword used inside an async function to pause the execution of the function until a Promise is resolved or rejected.
try…catch: A statement used to handle exceptions (errors) in JavaScript code, including within async functions.

Briefing Document: Asynchronous JavaScript and Module Management

This document provides a detailed review of the main themes and important ideas presented in the provided source materials, focusing on asynchronous JavaScript, module management in Node.js, and object-oriented programming concepts.

Part 1: Introduction to Node.js and Development Setup

Main Themes: Setting up a development environment with Node.js and Visual Studio Code (VS Code), basic JavaScript syntax, and an introduction to Object-Oriented Programming (OOP).

Key Ideas and Facts:

Node.js Installation: The document guides users through downloading and installing Node.js, recommending the default settings for most users.
“node.js once downloaded open the installer and follow the onscreen instructions the default settings are suitable for most users so you can proceed with them unless you have specific preferences”
VS Code Installation and Basic Usage: It provides instructions for downloading and installing VS Code, emphasizing that default settings are sufficient. Basic operations like creating a new project folder, adding files (.js extension is crucial), writing and saving code (Ctrl/Cmd + S), and executing JavaScript using the integrated terminal (node filename.js) are covered.
“the name of this file doesn’t matter but the file extension does”
“to save it I can do command s or on Windows it would be control s”
“I’ll type node and then the name of our file which is code. JS”
VS Code Interface Overview: The document introduces key components of the VS Code interface, including the activity bar (folder, search, source control, run and debug, extensions), status bar (errors/warnings, line number, language), command palette (Ctrl/Cmd + Shift + P), and basic customization options (color theme, text size).
“on the left hand side is the activity bar where we see a list of icons”
“on the bottom of the screen is the status bar here in Blue”
“you can access the command pallet by going to view and then command pallet now another way to do that is with the keyboard shortcut of command shift and P”
Recommended VS Code Extensions: Two extensions are recommended for the course: Live Server (for hot reloading in web development) and Quokka.js (for inline JavaScript output).
“for this course there are two vs code extensions that I suggest and that we will be using throughout this course so click on the icon for extensions and type in Live server then you can install this extension”
“another extension that we’ll be using for the early part of this course is quoka you type in quoka so select this one and then install it”
Introduction to OOP: The document introduces the fundamental concept of Object-Oriented Programming as a paradigm focused on organizing software design around “data or objects rather than focusing solely on functions and logic.” Objects are described as instances of classes, which serve as blueprints.
“objectoriented programming or o op is a programming Paradigm built around the concept of objects at its core oop organizes software design around data or objects rather than focusing solely on functions and logic objects are instances of classes which serve as blueprints for creating and managing data and”

Part 2: JavaScript Fundamentals and Object-Oriented Concepts

Main Themes: Data types, pass by value vs. pass by reference, dynamic nature of objects, loops, object literals, factory functions, constructor functions, the this keyword, prototypes, classes, static methods, abstraction, encapsulation, Getters and Setters, and property attributes.

Key Ideas and Facts:

Data Types: JavaScript supports eight data types: seven primitive (number, string, boolean, bigint, undefined, null, symbol) and one complex (object, including arrays and functions).
“JavaScript supports eight different data types which include seven primitive types and one complex type”
Pass by Value vs. Pass by Reference: Primitive types are passed by value (copied), so changes to one variable do not affect others. Reference types (objects, arrays, functions) are passed by reference (point to the same memory location), so changes in one variable are reflected in others.
“primitive types these are passed by value so when you work with primitive values these are passed by copy”
“reference types like objects are handled differently so they are passed by reference meaning both variables point to the same object in memory”
Dynamic Objects: JavaScript objects are dynamic, allowing properties and methods to be added, modified, or deleted after creation. Using const with an object prevents reassignment of the variable but not modification of the object’s contents.
“objects in JavaScript are inherently Dynamic which means that you can add or modify their properties and Methods at any time after their creation”
“using the cons keyword with an object declaration ensures that the variable cannot be reassigned to a different value however the contents of the object it points to such as its properties and methods can still be altered or extended”
Loops: The for…of loop is introduced as ideal for iterating over array elements.
“for arrays we can use the four of loop so the four of loop is ideal for ating over array elements”
Object Literals, Factory Functions, and Constructor Functions: The document explains different ways to create objects in JavaScript, including simple object literals, factory functions (returning objects), and constructor functions (using new and the this keyword).
The this Keyword: The behavior of this depends on how a function is called. In constructor functions, this refers to the newly created object. Detaching a method from its object can cause this to lose its original context (referring to the global object or undefined in strict mode).
“the this keyword in JavaScript behaves differently based on how a function is called This Behavior can lead to unexpected results especially when functions are detached from the object context”
Prototypes: Every object in JavaScript has a prototype (except the root object), which it inherits properties and methods from. Constructor functions have a prototype property that defines the prototype for all instances created with that constructor, optimizing memory usage by sharing methods.
“in JavaScript every object has a prototype except for the root object which is at the top of the Prototype chain the Prototype acts as a template or parent from which the object inherits methods and properties”
“Constructor functions have their own prototype in JavaScript functions are objects so they have their own prototype property which is used to assign properties and methods to instances created by the Constructor function”
Classes (ES6): ES6 introduced class syntax, which provides a more structured way to create objects and handle inheritance, implicitly using strict mode.
“if we were to to use classes they implicitly use strict mode to avoid these issues instead of using a Constructor function I’ll specify it to be a class”
Static Methods: Static methods are associated with the class itself, not instances of the class, and are called directly on the class.
“static methods are defined directly on the class itself and are called on the class rather than on an instance of the class”
Abstraction: Abstraction involves hiding complex implementation details and exposing only necessary parts through a public interface (e.g., public methods interacting with private methods). Private methods can be simulated using naming conventions (underscore prefix), Symbols (pseudo-private), or truly private class fields (using # prefix in ES2022+).
“abstraction and programming involves hiding complex implementation details and exposing only the necessary parts of an object this is commonly achieved through private properties and methods”
Encapsulation: Encapsulation is the bundling of data (properties) and methods that operate on the data, restricting direct access to some of the object’s components. This is achieved through private properties and methods, controlled access via Getters and Setters, and module scope.
Getters and Setters: Getters (get) and setters (set) are special methods used to control how object properties are accessed and modified, allowing for validation and encapsulation. Object.defineProperty (and Object.defineProperties) can be used to define these.
“Getters and sets are special methods that provide you with a way to get and set the properties of an object this encapsulation technique allows you to control how important values are accessed and modified in your objects it’s often used to ensure that data encapsulation and validation rules are followed”
Property Attributes (Descriptors): Properties have attributes (configurable, enumerable, writable) that determine if they can be deleted, iterated over, or modified. Object.defineProperty can be used to configure these attributes.
“configurable enumerable and writable for properties in our own objects”
“what are the property descriptors or attributes in JavaScript that determine whether a property can be accessed modified or iterated over in JavaScript property descriptors or attributes that determine whether a property can be accessed modified or iterated over are innumerable writable and configurable”
Closures: Closures are inner functions that have access to variables in their outer (enclosing) function’s scope, even after the outer function has finished executing. They are used to achieve encapsulation and create private variables.
“a closure means that inner function has access to variables declared in its outer function”
“closures are inner functions that are able to access variables defined in its outer function so in other words closure functions can access variables from their outer scope even after the outer function has finished executing now you would utilize closures in order to achieve encapsulation and to hide private variables or private properties”
WeakMap for Private Properties: WeakMap can be used to store private data in objects. Keys in a WeakMap are objects, and if an object key is garbage collected, its entry in the WeakMap is also removed, preventing memory leaks.
“weak Map is another way to implement private properties and methods in JavaScript classes”
“using weakmap for storing private data ensures that these details are not accessible from outside the class this is much more secure than using properties prefixed with an underscore”

Part 3: Module Management in Node.js

Main Themes: Understanding and using the Node.js module system (CommonJS and ES6 modules) for organizing and reusing code, global objects, and package management with npm.

Key Ideas and Facts:

Node.js as a Runtime Environment: Node.js allows JavaScript to run outside a web browser, primarily used for backend development (APIs, server-side applications). It uses an event-driven, non-blocking architecture.
“node.js is an open- Source cross-platform runtime environment that enables the execution of JavaScript outside of a web browser it’s primarily used for building servers set applications and networking tools”
Node.js Architecture and Features: Key features include its suitability for scalable, data-intensive, and real-time applications, quick startup and agility, real-world usage by major companies, the ability to use JavaScript for both frontend and backend, and a rich ecosystem (npm).
Runtime Environments: A runtime environment provides libraries and manages program execution. Web browsers have their own JavaScript engines (V8 in Chrome/Node.js, SpiderMonkey in Firefox, Chakra in Edge).
Node.js Module System (CommonJS): Each file in Node.js is treated as a separate module. require() is used to import modules, and module.exports (or exports) is used to export module contents.
“in node.js each file is treated as a separate module node.js provides a simple and efficient way to create modules and expose them to other parts of your application”
“node.js uses exports and module. exports to make functions and objects available to other files”
“we use the require function to include the module in another file”
Module Encapsulation (CommonJS): Modules in Node.js have their own scope, preventing global namespace pollution. Only explicitly exported items are accessible outside the module.
“one of the key benefits of using modules in nodejs is encapsulation by scope isolation each module has its own scope meaning its variables and functions are not accessible outside unless explicitly exported”
Exporting Defaults (CommonJS): module.exports = … is used to export a single default value (class, function, etc.).
“to export a class or function as the default export you use module. exports”
ES6 Modules: ES6 modules offer a more modern syntax for modularity in JavaScript (import and export).
“with es6 modules this provides a modern and cleaner syntax in order to achieve the same thing for JavaScript files that run in web browsers”
Global Objects in Node.js: Node.js provides built-in global objects (e.g., global, process, console, Buffer, timer functions) that are available in all modules. Custom global objects can be created by attaching properties to the global object.
“in nodejs Global objects are special objects that are available in all modules these objects provide essential functionality that could be access anywhere within a node.js application making them a fundamental part of the node.js runtime environment”
Loading Modules (require()): The require() function loads modules based on file paths. It’s best practice to use const when requiring modules to prevent accidental reassignment.
“nodejs uses the requir function to import modules which is a fundamental aspect of managing dependencies and modularity of your application”
“it’s a best practice to use the cons keyword as this prevents accidental reassignment of the module variable within your code”
Module Wrapping: Node.js wraps each module’s code in a function, providing scope isolation and access to module-specific variables (exports, require, module, __filename, __dirname).
“when node.js executes a module it does not run the code directly as written instead it wraps the module code inside a function this approach is not immediately apparent to the developer but it is fundamental to how nodejs operates”
OS Module: The built-in os module provides methods for retrieving system information (e.g., total memory, free memory).
“When developing applications that require system level data node.js provides a built-in module called OS which allows you to gather information about the underlying operating system”
FS (File System) Module: The built-in fs module allows interaction with the file system, providing synchronous (blocking) and asynchronous (non-blocking with callbacks or Promises) methods for file operations.
“node.js provides a powerful built-in module called FS for interacting with the file system this module is essential for reading from and writing to files on the server”
Package Management (npm): npm (Node Package Manager) is used to install, manage, and publish JavaScript packages. package.json file tracks project dependencies.
“npm which stands for node package manager which simplifies the addition of functionalities and accelerates the development process”
“npm is the default package manager for nodejs”
package.json: This file contains metadata about the project, including its name, version, dependencies, and scripts. npm init is used to create it.
“the package.json file is a central configuration file for your nodejs project it stores important metadata about your project such as its name version dependencies and scripts”
“you can initialize a new packagejson file by navigating to your project directory in the terminal and running the command mpm init”
Installing Packages (npm install): npm install <package-name> installs a package and adds it to node_modules and package.json (as a dependency). The –save-dev flag installs development dependencies.
“npm install <package-name> is the fundamental command used to install packages from the npm registry”
“to install a package as a development dependency which are tools needed for development and testing but not for running the application in production you can use the –save-dev flag”
node_modules: This directory stores all installed npm packages.
“npm installs these packages and their dependencies into a folder named nodeore modules in your project directory”
Version Control (Git and .gitignore): It’s crucial to exclude the node_modules directory from Git version control using a .gitignore file, as these dependencies can be restored using npm install.
“excluding known modules from Version Control is a best practice in nodejs development it keeps your project repository manageable speeds up operations like cloning and ensures that all developers are working with the same dependencies as defined in package.json”
Semantic Versioning (SemVer): Packages use semantic versioning (major.minor.patch) to indicate the type of changes in updates, helping developers understand the potential impact of updating dependencies. Carrots (^) and tildes (~) in package.json specify acceptable ranges for automatic updates.
“semantic versioning is a standard for versioning software which is widely adopted in the development Community including nodejs packages it helps developers understand the potential impact of updating a package”
Global npm Packages: Packages installed globally (npm install -g <package-name>) are typically command-line tools accessible system-wide. Minimize global installations to avoid version conflicts.
“Global packages are typically command line tools or utilities that you want to run from anywhere on your system not just within a specific project”
“to install a package globally you would use the – G or hyphen G or the– Global flag with the mpm install command”
Publishing npm Packages: The process involves setting up a package.json with a unique name, creating an npm account, writing the package code, and using npm publish to share it. Updates require incrementing the version in package.json.
“creating and Publishing your own mpm package can be a rewarding process allowing you to share your work with the wider no. JS community”
“to publish your package to mpm using the command mpm publish”

Part 4: Asynchronous JavaScript

Main Themes: Understanding synchronous vs. asynchronous code execution, and the evolution of patterns for handling asynchronous operations: callbacks, Promises, and async/await.

Key Ideas and Facts:

Synchronous vs. Asynchronous Code: Synchronous code executes sequentially, blocking further execution. Asynchronous code allows other operations to continue while waiting for a task to complete.
“understanding the difference between synchronous and asynchronous code is fundamental in JavaScript synchronous code executes sequentially blocking further execution until the current task is completed in contrast a synchronous code allows other operations to continue while waiting for an asynchronous task to complete improving performance and responsiveness”
Callbacks: Functions passed as arguments to be executed upon completion of an asynchronous operation. Nested callbacks can lead to “callback hell” (deeply nested and hard-to-manage code). Named functions can improve readability of callback-based code.
“a call back is a function that is passed as an argument to another function to be executed once an asynchronous operation is complete”
“nested callbacks which can lead to callback how which is a situation where code becomes deeply nested and difficult to manage this pattern complicates both reading and maintaining the code”
Promises: Objects representing the eventual outcome (success or failure) of an asynchronous operation. They have three states: pending, fulfilled (resolved), and rejected. Promises provide a cleaner way to handle asynchronous logic using .then() for success and .catch() for errors, avoiding callback hell. Promise.resolve() and Promise.reject() create pre-resolved or pre-rejected promises. Promises support running asynchronous operations in parallel using Promise.all().
“JavaScript promises are a powerful tool for managing asynchronous operations A promise is an object that represents the eventual result of an asynchronous operation it can be in one of three states the first being pending so this is the initial State when the promise is still waiting for the asynchronous operation to complete the second state is fulfilled the operation completed successfully and the promise has a value and the third possible state is rejected so the operation failed and the promise hasn’t air”
“replacing callbacks with promises promises help avoid the complexity of nested callbacks by returning promises from functions you can chain asynchronous operations more straightforward using the them method for resolve promises and do catch for errors”
Async/Await: Syntactic sugar over Promises that makes asynchronous code look and behave more like synchronous code. async declares an asynchronous function (which implicitly returns a Promise), and await pauses the execution of an async function until a Promise resolves. Error handling with async/await is done using try…catch blocks.
“async 08 is syntactic suar sugar over promises making asynchronous code look synchronous”
“this keyword allows you to wait for a promise to resolve and get its result you could use it only inside functions marked with the async keyword”
“async this keyword is used to declare that a function is asynchronous it ensures that the function returns a promise”
“for air handling we use try and catch blocks to handle errors when using a sync and a we”

This briefing document covers the foundational concepts and practices discussed in the provided sources, highlighting the setup of a development environment, core JavaScript principles, object-oriented programming, module management in Node.js, and effective strategies for handling asynchronous operations. Understanding these topics is crucial for modern JavaScript development, particularly in backend environments using Node.js.

Frequently Asked Questions on Node.js and JavaScript Asynchronous Programming

1. What are the fundamental differences between synchronous and asynchronous code execution in JavaScript, and why is understanding this distinction important for Node.js development?

Synchronous code executes line by line, and each operation must complete before the next one begins, potentially blocking the program if an operation takes a long time. Asynchronous code, on the other hand, allows the program to continue executing other tasks while waiting for a long-running operation (like reading a file or a network request) to complete. Once the asynchronous operation finishes, a callback function or a promise’s resolution/rejection is handled. Understanding this distinction is crucial for Node.js development because Node.js is designed to handle many concurrent connections efficiently. Its non-blocking, event-driven architecture relies heavily on asynchronous operations to prevent the server from becoming unresponsive when dealing with I/O-bound tasks.

2. How does Node.js utilize modules to organize and encapsulate code, and what are the advantages of this modular approach for building scalable and maintainable applications?

Node.js treats each file as a separate module, helping to organize code into reusable units. Modules can export specific parts of their functionality (functions, objects, classes) using module.exports (in CommonJS) or export (in ES Modules), which can then be imported into other modules using require (in CommonJS) or import (in ES Modules). This modular approach offers several advantages:

Code Organization: It breaks down large applications into smaller, manageable pieces, making the codebase easier to navigate and understand.
Reusability: Modules can be reused across different parts of the application or even in other projects, reducing code duplication and development time.
Maintainability: Changes to one module are less likely to affect other parts of the application, provided the module’s interface remains stable, making it easier to update and refactor code.
Scalability: Well-organized, modular code is easier to scale as new features or functionalities can be added as separate modules without increasing the complexity of the entire system.
Namespace Management: Modules help avoid global namespace pollution by keeping variables and functions within their local scope unless explicitly exported.

3. What is the Node Package Manager (npm), and why is it an essential tool for Node.js development? What are some key commands and concepts associated with npm?

npm (Node Package Manager) is the default package manager for Node.js. It is an essential tool that allows developers to easily share, install, and manage dependencies (third-party libraries and tools) for their Node.js projects. Key commands and concepts include:

npm init: Initializes a new Node.js project and creates a package.json file.
package.json: A file that contains metadata about the project, including its name, version, dependencies, scripts, and more. It’s crucial for managing project dependencies.
npm install <package-name>: Installs a specified package and adds it to the node_modules directory and the dependencies or devDependencies section of package.json.
npm install -D <package-name> or npm install –save-dev <package-name>: Installs a package as a development dependency, typically used for testing or build tools.
npm install: Installs all the dependencies listed in the package.json file.
node_modules: The directory where npm installs project dependencies. It’s typically excluded from version control.
Semantic Versioning (semver): A standard (Major.Minor.Patch) used by npm to manage package versions and specify compatible update ranges using symbols like ^ (caret) and ~ (tilde) in package.json.
Global vs. Local Installations: Packages can be installed locally (within a project’s node_modules) or globally (for command-line tools accessible system-wide using npm install -g <package-name>).
npm publish: Used by developers to upload their own packages to the npm registry for others to use.

4. How does Node.js handle asynchronous operations using callbacks, promises, and async/await? What are the benefits and drawbacks of each approach, and when might you choose one over the others?

Node.js provides several ways to handle asynchronous operations:

Callbacks: Functions passed as arguments to be executed upon the completion of an asynchronous task.
Benefits: Widely supported and the original way of handling asynchronicity in JavaScript.
Drawbacks: Can lead to “callback hell” (deeply nested callbacks) making code hard to read and maintain. Error handling can become complex.
When to use: For simple asynchronous operations or when working with older APIs that don’t support promises.
Promises: Objects representing the eventual completion (resolve) or failure (reject) of an asynchronous operation. They provide a more structured way to handle asynchronicity using .then() for success and .catch() for errors.
Benefits: Improve code readability and maintainability by avoiding callback hell through chaining. Offer better error handling with a single .catch() at the end of a promise chain.
Drawbacks: Can still lead to verbose code with long chains. Error handling needs to be explicitly managed.
When to use: For managing sequences of asynchronous operations or when dealing with APIs that return promises.
Async/Await: Syntactic sugar built on top of promises that allows you to write asynchronous code that looks and behaves more like synchronous code using the async and await keywords.
Benefits: Significantly improves code readability and makes asynchronous logic easier to follow. Simplifies error handling using try…catch blocks.
Drawbacks: await can only be used inside async functions. Can sometimes hide the asynchronous nature of operations, potentially leading to misunderstandings about performance.
When to use: For most modern asynchronous JavaScript development where readability and maintainability are key, especially for complex sequences of asynchronous tasks.

5. What is the significance of the this keyword in JavaScript, and how does its behavior differ in various contexts (e.g., global scope, function context, class methods, arrow functions)? How can issues related to this context be managed?

The this keyword in JavaScript refers to the object that is currently executing the code. Its behavior varies depending on the context in which it is used:

Global Scope: In non-strict mode, this refers to the global object (e.g., window in browsers, global in Node.js). In strict mode, this is undefined.
Function Context (Regular Functions): The value of this depends on how the function is called. It can be the global object (in non-strict mode when called independently), undefined (in strict mode when called independently), the object calling the method (when called as a method of an object), or bound to a specific object using call(), apply(), or bind().
Class Methods: Inside methods of a class, this refers to the instance of the class that the method is called on.
Arrow Functions: Arrow functions do not have their own this context. They lexically capture the this value from their surrounding (enclosing) scope. This makes them useful for callbacks within methods or other functions where you want this to refer to the outer scope’s this.

Issues related to this context can be managed by:

Using arrow functions to preserve the this from the outer scope.
Using bind(), call(), or apply() to explicitly set the this value.
Being mindful of strict mode’s impact on this in regular functions.
When detaching methods from objects, ensure the intended this context is preserved (e.g., using bind()).

6. Explain the concepts of closures, encapsulation, and abstraction in JavaScript. How are these principles implemented and why are they important for writing robust and maintainable code, especially in the context of object-oriented programming with Node.js?

Closures: A closure is a feature in JavaScript where an inner function has access to the outer (enclosing) function’s variables—the scope chain—even after the outer function has finished executing. This happens because the inner function “closes over” its environment. Closures are often used to create private variables and maintain state.
Encapsulation: Encapsulation is the practice of bundling data (properties) and the methods that operate on that data within a single unit (an object or a module). It also involves hiding the internal state of an object and exposing only a public interface. This protects the data from unintended modification and simplifies how the object is used. In JavaScript, encapsulation can be achieved using closures (for data privacy), conventions (like prefixing private members with _), Symbols, WeakMaps, and private class fields (#). Modules also provide encapsulation by isolating the scope of variables and functions.
Abstraction: Abstraction involves hiding complex implementation details and showing only the essential information to the user. It allows developers to use objects or modules without needing to know how they work internally. In JavaScript, abstraction can be implemented through well-defined public interfaces of objects and modules, which internally use private properties and methods (achieved through closures, Symbols, WeakMaps, or private class fields) to handle the complexity.

These principles are crucial for writing robust and maintainable code because they:

Improve Code Organization: They help structure code logically, making it easier to understand and manage.
Enhance Reusability: Encapsulated and abstracted components are more likely to be reusable in different parts of the application or in other projects.
Increase Maintainability: Changes to the internal implementation of an encapsulated component do not affect other parts of the system as long as the public interface remains the same.
Promote Data Integrity: Encapsulation helps protect data by controlling how it can be accessed and modified.
Reduce Complexity: Abstraction allows developers to work with higher-level concepts without being overwhelmed by the underlying details.

In Node.js, which is often used to build complex backend systems, applying these OOP principles helps manage the complexity of the application and ensures that the codebase remains manageable as it grows.

7. What are prototypes and how does prototype-based inheritance work in JavaScript? How do constructors relate to prototypes, and why is understanding the prototype chain important for optimizing memory usage and code reuse in Node.js applications?

In JavaScript, every object has a prototype, which is another object that it inherits properties and methods from. This is the basis of prototype-based inheritance. When you try to access a property of an object, and that property is not found on the object itself, JavaScript looks up the prototype chain until it finds the property or reaches the end of the chain (which is null).

Constructors are functions used to create objects. When you create an object using the new keyword with a constructor function, the newly created object’s internal prototype ([[Prototype]], accessible via __proto__ or Object.getPrototypeOf()) is set to the prototype property of the constructor function.

Understanding the prototype chain is important for:

Memory Optimization: Methods and properties added to the prototype of a constructor are shared by all instances created by that constructor. This means that instead of each object having its own copy of these members, they all refer back to the same ones on the prototype, saving memory, especially when dealing with a large number of objects.
Code Reuse: Inheritance through prototypes allows you to reuse functionality defined on a prototype across multiple objects, promoting a more organized and efficient codebase. You can extend or modify the behavior of objects by manipulating their prototypes.
Understanding JavaScript’s Object Model: A solid grasp of prototypes is fundamental to understanding how objects in JavaScript work and how inheritance is achieved.

In Node.js, where applications often involve creating many objects (e.g., handling numerous requests), leveraging prototype-based inheritance effectively can lead to significant performance improvements and more efficient resource utilization.

8. What are ES Modules and CommonJS, and how do they differ in Node.js? What are the syntaxes for importing and exporting modules in each system, and when might you choose one over the other in a Node.js project?

CommonJS was the original module system used in Node.js. It uses a dynamic approach to module loading.

Exporting: Uses module.exports to export values (can be a single value or an object containing multiple exports) and exports as a shorthand for module.exports.
Importing: Uses the require() function to import modules, typically assigning the result to a variable.

ES Modules (ECMAScript Modules) are the standard module system introduced in ECMAScript 2015 (ES6). They offer a more static and standardized way to handle modules across JavaScript environments (browsers and Node.js).

Exporting: Uses the export keyword to export named bindings (e.g., export const myVariable = …) or a default export (e.g., export default myClass).
Importing: Uses the import keyword to import named bindings (e.g., import { myVariable } from ‘./module’) or the default export (e.g., import myClass from ‘./module’).

Differences in Node.js:

Loading Mechanism: CommonJS is dynamic (modules are resolved at runtime), while ES Modules are more static (module dependencies can be analyzed at parse time, allowing for potential optimizations like tree-shaking).
Syntax: Different keywords (require/module.exports vs. import/export).
Scope: Both provide module-level scope, but ES Modules have stricter scoping rules.
“use strict”: ES Modules implicitly operate in strict mode.
Top-level await: Allowed in ES Modules but not in CommonJS (outside of async functions).

When to Choose:

CommonJS: Historically used in most Node.js projects and is still the default in many older projects or when working with code that primarily uses this syntax.
ES Modules: Recommended for new Node.js projects as they are the modern JavaScript standard and offer benefits like static analysis and better support in modern JavaScript tooling. Node.js has increasingly improved its support for ES Modules, and it’s becoming more common to use them. You can configure Node.js to treat .js files as ES Modules by adding “type”: “module” to your package.json file, or by using the .mjs file extension.

Many modern Node.js projects are transitioning to or already using ES Modules for a more standardized and potentially optimized module management system.

JavaScript OOP Challenges and Considerations

Object-Oriented Programming (OOP), while offering numerous benefits, also presents certain challenges, particularly in its implementation and design. Based on the sources, some of these challenges in the context of JavaScript include:

Challenges with Inheritance:
Inappropriate Relationships: A key challenge with inheritance is ensuring that the subclass truly represents a specialized version of the superclass, adhering to the “is a” relationship. Problems arise when a subclass inherits methods that do not logically apply to it, leading to an inappropriate relationship and potentially bloated or confusing interfaces. For example, if a base Employee class has a code method, it might not logically apply to a Manager subclass.
Inheritance Complexity: Deep inheritance hierarchies can become difficult to manage and understand. The more levels of inheritance, the harder it can be to track where properties and methods are coming from and how changes in one part of the hierarchy might affect others. The sources suggest limiting inheritance depth to maintain manageable code.
Constructor Property Issues: When implementing inheritance using Object.create to set the prototype, the constructor property of the subclass prototype mistakenly points to the superclass constructor. This can cause confusion when creating instances dynamically and requires manually resetting the constructor property to reflect the actual subclass constructor.
Modifying Built-in Prototypes: While JavaScript allows extending built-in prototypes, it is generally ill-advised due to the potential for conflicts with third-party libraries that might rely on the default behavior. Modifying built-in prototypes can also lead to inconsistent behavior and make code harder to maintain and predict, potentially breaking compatibility with future JavaScript versions.
Global Scope Pollution: In JavaScript environments, particularly browsers, defining variables and functions in the global scope (using var at the top level) can lead to namespace pollution. The global namespace can become cluttered, making it difficult to track definitions. Additionally, accidental overwriting of global variables by different parts of an application can cause hard-to-diagnose bugs. Modularity, using techniques like CommonJS or ES6 modules, is essential to mitigate these risks by encapsulating code and avoiding global scope interference.
Managing Private Data: Achieving true data encapsulation, a core OOP principle, has historically been a challenge in JavaScript. While naming conventions (using underscores) and ES6 Symbols offer some level of privacy, they don’t provide complete protection. ES2022 introduced private class fields (using the # prefix) as a more robust solution for ensuring data and method privacy within classes. WeakMap can also be used to store private data, offering the additional benefit of allowing objects to be garbage collected even with associated private data in the WeakMap.
Choosing Between Inheritance and Composition: Deciding when to use inheritance versus composition can be a challenge. Inheritance should ideally represent an “is a” relationship, but over-reliance can lead to complex hierarchies and the inheritance of inappropriate functionalities. Composition, representing a “has a” relationship, often provides a more flexible and robust alternative by building objects from components, reducing dependencies and promoting code reuse through techniques like mixins.

These points highlight some of the significant challenges and considerations when working with OOP principles in JavaScript, emphasizing the importance of careful design, adherence to best practices, and understanding the specific features and limitations of the language.

JavaScript Objects: Concepts and Mechanisms

Let’s discuss JavaScript objects, drawing on the information from the sources and our previous conversation about OOP challenges.

Fundamentals of JavaScript Objects

At its core, a JavaScript object is a collection of key-value pairs. These pairs are also known as properties, where the key is typically a string (or Symbol) and the value can be any JavaScript data type, including primitive values, other objects, or functions. Functions within an object are referred to as methods.

Creating Objects

JavaScript offers several ways to create objects:

Object Literals: The most common way to create a simple object is using curly braces {} to define an object literal, where you directly specify the key-value pairs. For example:
let programmer = {
name: “Steven Garcia”,
preferredLanguage: “JavaScript”,
writeCode: function() {
console.log(this.name + ” writes ” + this.preferredLanguage + ” code”);
},
drinkCoffee() { // Syntactic sugar for defining methods
console.log(this.name + ” drinks coffee”);
}
};
Factory Functions: A factory function is a function that returns a new object each time it is called. This can help avoid code duplication when creating multiple similar objects.
Constructor Functions: Before ES6, JavaScript used constructor functions along with the new keyword to create objects, mimicking class-like behavior. Constructor functions use PascalCase for naming convention, and the this keyword is used to assign properties and methods to the new object.
ES6 Classes: Introduced in ES6, the class syntax provides a more structured and cleaner way to define constructor functions and manage prototypical inheritance. It is essentially syntactic sugar over JavaScript’s existing prototypal inheritance model. Classes use a constructor method to initialize object properties and define methods within the class body.

Dynamic Nature of Objects

JavaScript objects are inherently dynamic, meaning you can add, modify, and delete properties and methods at any time after an object’s creation. This can be done using either dot notation or square bracket notation. While using const to declare an object prevents reassignment of the variable to a different object, the contents of the object itself can still be altered.

Iterating Over Object Properties

JavaScript provides several ways to iterate over the properties of an object:

for…in loop: This loop iterates over all enumerable properties of an object, including inherited properties from its prototype chain.
Object.keys(obj): This method returns an array containing the names of all own enumerable properties of the object obj. It does not include inherited properties.
Object.values(obj): This method returns an array containing the values of all own enumerable properties of the object obj.
Object.entries(obj): This method returns an array of [key, value] pairs for all own enumerable properties of the object obj.

Prototypes and Prototypal Inheritance

Every JavaScript object has an internal prototype (accessible via Object.getPrototypeOf(obj) or the older __proto__ property), which is another object or null. When you try to access a property of an object, and that property is not found on the object itself, JavaScript looks for it in the object’s prototype, then in the prototype’s prototype, and so on, up the prototype chain. This mechanism is known as prototypal inheritance, where objects inherit properties and methods from their prototype objects.

Constructor functions also have a prototype property, which is an object that becomes the prototype for all instances created with that constructor. Methods defined on a constructor’s prototype are shared among all instances, leading to more memory-efficient code compared to defining methods directly within the constructor function.

The this Keyword

The this keyword in JavaScript refers to the context in which a function is executed. In the context of object methods, this typically refers to the object that the method is called on. However, the value of this can change depending on how a function is called (e.g., direct function call, method call, using call, apply, or bind). In strict mode, the value of this in a standalone function is undefined, which helps prevent accidental modification of the global object. ES6 classes implicitly use strict mode.

Encapsulation and Data Privacy

Encapsulation, one of the four pillars of OOP, involves hiding the internal state and functionality of an object and exposing only what is necessary. JavaScript provides several mechanisms for achieving data privacy:

Abstraction: Hiding complex implementation details and showing only necessary information to the user. This is often achieved through well-defined public interfaces (methods) that interact with private parts of the object.
Naming Conventions (Underscore Prefix): Historically, using an underscore _ prefix for property names was a convention to indicate that a property was intended for internal use and should not be accessed directly from outside the object. However, this does not provide true privacy.
Symbols: ES6 introduced Symbols, which are unique and immutable primitive values that can be used as object property keys. Properties keyed by Symbols are not easily discoverable through standard reflection mechanisms, providing a form of “soft” privacy.
Weak Maps: WeakMap is a collection of key-value pairs where keys are objects, and values are arbitrary values. Unlike regular Maps, WeakMap allows for garbage collection of key objects even if they are still present as keys in the WeakMap (if there are no other strong references to them). This makes them suitable for storing private data associated with objects without preventing memory leaks.
ES2022 Private Class Fields: ES2022 introduced private class fields and methods using the hash # prefix. These private members are truly private and are only accessible from within the class where they are defined, providing strong data encapsulation.

Inheritance and Extending Objects

JavaScript primarily uses prototypal inheritance for sharing properties and methods between objects. ES6 classes provide a more familiar syntax for defining inheritance hierarchies using the extends keyword. A subclass (or derived class, child class) can extend a superclass (or base class, parent class), inheriting its properties and methods.

The super keyword is used in a subclass constructor to call the superclass constructor and in subclass methods to call superclass methods, allowing for extending or modifying inherited behavior.
Method overwriting allows a subclass to provide its own specific implementation of a method that is already defined in its superclass.

Mixins

Mixins offer a flexible alternative to traditional inheritance for composing objects with multiple behaviors. Instead of inheriting from a single base class, an object can “mix in” functionalities from multiple smaller, focused objects. This can be achieved using Object.assign to copy properties and methods from mixin objects to a target object. Mixins promote composition over inheritance, which can lead to more modular and maintainable code.

Property Descriptors

JavaScript objects have associated property descriptors that define the attributes of each property, controlling how they can be accessed, modified, and enumerated. These attributes include:

enumerable: Determines whether the property will appear during for…in loops and Object.keys().
writable: Determines whether the property’s value can be changed.
configurable: Determines whether the property descriptor can be changed and whether the property can be deleted.

You can get and set these attributes using Object.getOwnPropertyDescriptor() and Object.defineProperty() respectively.

Getters and Setters

Getters and Setters are special methods that allow you to control the access and modification of object properties.

Getters (defined using the get keyword in object literals or class bodies, or Object.defineProperty) are called when you try to access a property, allowing you to execute code and return a computed value.
Setters (defined using the set keyword or Object.defineProperty) are called when you try to assign a value to a property, allowing you to perform actions like validation or logging before the value is actually set.

Getters and Setters provide a way to encapsulate property access and modification, enhancing data integrity and providing a cleaner interface.

Primitive vs. Reference Types

It’s important to understand that objects are reference types in JavaScript. When you assign an object to a variable, you are actually assigning a reference to the object in memory. If you assign that variable to another variable, both variables will point to the same object in memory. Therefore, changes made through one variable will affect the other. This is in contrast to primitive types (e.g., numbers, strings, booleans), which are passed by value, meaning a copy of the value is created when assigned to a new variable.

Memory Management

As we discussed, using prototypes for shared methods is crucial for memory efficiency when dealing with numerous object instances. Instead of each instance having its own copy of a method, they all share the same method defined on the prototype. Additionally, using WeakMap for private data can aid in memory management by allowing the garbage collector to reclaim memory occupied by objects even if they have associated private data in the WeakMap (when there are no other strong references).

By understanding these concepts, you can effectively work with JavaScript objects, leveraging their flexibility and power while also being mindful of best practices for code organization, maintainability, and performance, especially in the context of the OOP challenges we previously discussed.

JavaScript Object Literals: Definition and Use

Let’s delve deeper into JavaScript object literals, drawing upon the information in the provided sources and our previous discussion about JavaScript objects.

An object literal is a fundamental way to create objects in JavaScript. It is defined using curly braces {} and consists of key-value pairs. These key-value pairs represent the properties of the object, where the key is typically a string (or Symbol) and the value can be any valid JavaScript data type, including primitive values, other objects, or functions (which become methods of the object).

Creating Object Literals

You create an object literal by simply using the curly brace notation and defining the key-value pairs within them. Here’s a basic example from source:

let proProgrammer = {

name: “Your Name”,

preferredLanguage: “JavaScript”

};

In this example, proProgrammer is an object literal with two properties: name and preferredLanguage, each assigned a string value.

Defining Properties and Methods

Within an object literal, you can define both data properties and methods.

Properties are defined as key: value pairs.
Methods (functions associated with the object) can be defined in a couple of ways:
Using a traditional function expression:
let myObject = {
myMethod: function() {
// … function body
}
};
Using the more concise syntactic sugar introduced in ES6:
let myObject = {
myMethod() {
// … function body
}
};

Source provides an example illustrating method definition:

let programmer = {

name: “Steven Garcia”,

preferredLanguage: “JavaScript”,

writeCode: function() {

console.log(this.name + ” writes ” + this.preferredLanguage + ” code”);

drinkCoffee() { // Syntactic sugar

console.log(this.name + ” drinks coffee”);

}

};

Here, writeCode and drinkCoffee are methods of the programmer object literal. The this keyword within these methods refers to the programmer object itself, allowing access to its properties like name.

Dynamic Nature

As we discussed previously, and as implied by the ability to manipulate objects using dot or bracket notation, object literals, like all JavaScript objects, are dynamic. You can add new properties or methods, modify existing ones, or delete them after the object literal has been created. For example:

let myObject = { key: “value” };

myObject.newProperty = “another value”; // Adding a new property

myObject.key = “updated value”; // Modifying an existing property

delete myObject.key; // Deleting a property

Use Cases and Benefits

Object literals are incredibly useful for:

Organizing related data: They allow you to group together a set of variables (properties) and functions (methods) that logically belong together, as seen in the programmer example.
Representing real-world entities or complex data models: You can easily model objects with their attributes and behaviors using object literals.
Creating simple configuration objects: Passing options or settings to functions often involves using object literals.
Returning simple data structures from functions.

Source highlights that by using object literals, you can create versatile and reusable code structures that represent real-world entities or complex data models effectively. They contribute to making your code cleaner and more intuitive to work with by encapsulating related properties and functions within a single organized entity.

Limitations

While object literals are convenient, they have limitations, especially when you need to create multiple objects with the same structure and methods. Source points out that if you need to create multiple programmer objects using the object literal syntax repeatedly, it can lead to duplicated code, making your application harder to maintain. This is particularly true for objects that include methods, as the behavior might be repeated across multiple instances.

Comparison with Other Object Creation Methods

To address the code duplication issue with object literals, JavaScript offers other ways to create objects, such as:

Factory Functions: As mentioned in source, factory functions are functions that return a new object each time they are called, allowing for the creation of multiple objects with the same methods but potentially different property values.
Constructor Functions (and ES6 Classes): These provide a blueprint for creating objects and are particularly useful for implementing inheritance and creating instances of a specific “type” of object, as discussed in sources.

In summary, object literals are a foundational and highly used feature in JavaScript for creating single instances of objects with a clear and concise syntax. They are excellent for organizing data and representing entities but can become less maintainable when you need to create many similar objects, at which point factory functions or constructor functions/classes might be more appropriate.

JavaScript Factory Functions: Object Creation Pattern

Let’s delve into Factory Functions in JavaScript, drawing upon the information in the provided sources and our previous discussion about object literals.

A factory function in JavaScript is essentially a function that returns a new object each time it is called. Source explains that the name of a factory function is typically in camel case notation and that it can accept parameter variables. These parameters allow you to customize the values of the object being returned.

Creating Factory Functions

According to source, you implement a factory function as a regular JavaScript function. Inside this function, you define and return a new object literal. Here’s the example provided in source for creating programmer objects:

function createProgrammer(name, preferredLanguage) {

return {

name,

preferredLanguage,

writeCode: function() {

console.log(this.name + ” writes ” + this.preferredLanguage + ” code”);

drinkCoffee: function() {

console.log(this.name + ” drinks coffee”);

}

};

}

In this example, createProgrammer is a factory function that takes name and preferredLanguage as parameters and returns a new object literal with these properties and the writeCode and drinkCoffee methods. Source also demonstrates a more concise syntax for the returned object literal:

function createProgrammer(name, preferredLanguage) {

return {

name,

preferredLanguage,

writeCode() {

console.log(this.name + ” writes ” + this.preferredLanguage + ” code”);

drinkCoffee() {

console.log(this.name + ” drinks coffee”);

}

};

}

Source also provides an example of a factory function for creating grocery list items:

function createGroceryItem(name, quantity) {

return {

name,

quantity,

display() {

console.log(this.quantity + ” times ” + this.name);

}

};

}

Benefits of Using Factory Functions

Source explicitly states the benefit of factory functions is that they reduce code duplication and the need to copy and paste when you need to create multiple objects with similar structures and behaviors.

Consider the limitation of object literals we discussed earlier. If you needed to create several programmer objects, using object literals would require you to duplicate the writeCode and drinkCoffee methods in each object, making the code inefficient and harder to maintain. Factory functions solve this problem because the methods are defined once within the factory function and are included in each new object it returns. This makes the codebase cleaner and more manageable.

Source further elaborates that factory functions provide an efficient way to create new objects. The parameter variables allow for customizing the values of the returned object.

Usage

To use a factory function, you simply call it like any other function, passing in the necessary arguments. Source provides the following examples:

For the programmer factory:

const newProgrammer = createProgrammer(“Alice”, “JavaScript”);

newProgrammer.writeCode(); // Output: Alice writes JavaScript code

For the grocery list item factory:

const newItem = createGroceryItem(“bananas”, 5);

newItem.display(); // Output: 5 times bananas

In summary, factory functions are a valuable pattern in JavaScript for creating multiple objects with shared behavior without duplicating code. They enhance maintainability and provide a cleaner way to instantiate objects compared to repeatedly using object literals, especially when those objects have methods. They offer a step towards more structured object creation in JavaScript.

JavaScript Constructor Functions

Let’s discuss Constructor functions in JavaScript, drawing upon the information in the provided sources and our conversation history about object literals and factory functions.

In traditional JavaScript, before the introduction of the class syntax in ES6, constructor functions were the standard way to mimic class-like behavior and instantiate new objects. Source explicitly states that JavaScript used functions and the new keyword to achieve this, a technique known as Constructor functions. The ES6 class syntax, as source notes, is essentially syntactic sugar over this underlying prototypal inheritance mechanism.

Defining Constructor Functions

According to source, constructor functions are defined using the function keyword. By convention, their names are written in PascalCase, where the first letter of each word in the name is capitalized (e.g., Programmer, GroceryItem).

Here’s an example from source of a constructor function for creating programmer objects:

function Programmer(name, preferredLanguage) {

this.name = name;

this.preferredLanguage = preferredLanguage;

this.writeCode = function() {

console.log(this.name + ” writes ” + this.preferredLanguage + ” code”);

};

this.drinksCoffee = function() {

console.log(this.name + ” drinks coffee”);

};

}

And here’s a constructor function for a grocery item from source:

function GroceryItem(name, quantity) {

this.name = name;

this.quantity = quantity;

this.display = function() {

console.log(this.quantity + ” times ” + this.name);

};

}

The new Keyword

The crucial aspect of constructor functions is how they are used to create objects. You instantiate a new object and call a constructor function using the new keyword.

When you use new followed by a constructor function:

A new object is created in memory.
The this keyword inside the constructor function is bound to this newly created object.
The code inside the constructor function is executed, allowing you to assign properties and methods to the this object.
If the constructor function does not explicitly return an object, the newly created object is returned implicitly.

Source provides an example of creating instances using the new keyword:

const newProgrammer = new Programmer(“Alice”, “JavaScript”);

newProgrammer.writeCode(); // Output: Alice writes JavaScript code

const newItem = new GroceryItem(“bananas”, 5);

newItem.display(); // Output: 5 times bananas

The this Keyword

As mentioned above, within a constructor function, the this keyword refers to the specific instance of the object being created. This allows you to assign properties (like this.name = name) and define methods (like this.writeCode = function() {…}) that will belong to each individual object created with the constructor.

The constructor Property

Every object in JavaScript has a special property called constructor. This property references the function that was used to create the object via the new keyword. Source illustrates this:

console.log(newProgrammer.constructor); // Output: [Function: Programmer]

This constructor property can be useful for checking the type of an object, especially in more complex codebases.

Comparison with Object Literals and Factory Functions

Object Literals: As we discussed, object literals are excellent for creating single, specific objects. However, when you need to create multiple objects with the same structure and methods, they lead to code duplication. Constructor functions (and factory functions) address this by providing a reusable blueprint.
Factory Functions: Both constructor functions and factory functions serve to create multiple objects. However, they differ in their approach:
Constructor functions are called with the new keyword, and they implicitly return the newly created object. The this keyword is central to their operation.
Factory functions are regular functions that explicitly return a new object literal. They don’t require the new keyword, and the concept of this refers to the scope in which the function is called unless explicitly bound. Source mentions that factory functions ensure each object has its unique properties but can share the same methods. We will likely discuss how method sharing is typically implemented with constructor functions (using prototypes) later.

In summary, constructor functions provide a way to create multiple objects with a defined structure and behavior. They rely on the new keyword to instantiate objects and bind the this keyword to the new instance. They were a fundamental pattern in JavaScript for creating objects that share properties and methods before the introduction of the more class-like syntax in ES6.

JavaScript Essentials Course

The Original Text

learn JavaScript Essentials with this course that covers everything from objectoriented programming fundamentals to Advanced asynchronous Techniques Steph Garcia will teach you critical Concepts including objects prototypes es6 classes modules and the node ecosystem while building practical skills through Hands-On examples welcome to JavaScript Pro the comprehensive course designed to take you from intermediate to advanced level JavaScript JavaScript is everywhere from Dynamic websites to mobile apps mastering it is the key to unlocking opportunities as a developer this isn’t just another JavaScript course it’s a step-by-step guide into the features of the JavaScript language this course is for developers looking to level up their skills what truly sets this course apart is our teaching style I use the active recall technique popularized by Cal Newport the author of deep work and a computer science Professor this technique engages your brain in a way that helps you truly internalize concepts by actively practicing how to retrieve them from memory in every section you’ll encounter carefully crafted study questions designed not just to teach but also to challenge you we’ll go over a possible answer for every single question helping you fill in any gaps of your understanding plus there’s an accompanying ebook and PDF that includes all the questions and answers so you can review and reinforce your knowledge anytime this course is designed to actively engage all learning styles visual auditory reading and kinesthetic so that no matter how you learn best you’ll find an approach that works for you every lesson is structured to utilize multiple senses and areas of the brain to maximize retention and understanding we start with the fundamentals of advanced JavaScript covering objectoriented programming prototypes es6 classes and modules you’ll dive into practical tools like Babel webpack and node.js to build projects that mirr world world scenarios my goal is to teach you how to think like a professional developer by the end of this course you’ll have the skills confidence and mindset needed to tackle complex JavaScript problems Ace job interviews and have the fundamental programming skills needed to build apps so let’s go over what you’ll learn in the nine sections of JavaScript Pro intro to Advanced topics we start with the essentials an introduction to Advanced JavaScript Concepts and how this course is structured to maximize your learning you’ll set up a professional development environment and gain an overview of the key skills you’ll develop throughout the course this section lays the foundation for a smooth productive learning experience objects Master the core principles of objectoriented programming also referred to as o including the four pillars which are encapsulation inheritance abstraction and polymorphism you’ll learn how to create and manipulate objects using different approaches like object literals factories and Constructors by the end of the section you’ll understand how to manage properties use Getters and Setters and handle Concepts like abstraction and private properties which are all critical for building scalable and maintainable code prototypes discover how javascripts prototypical inheritance Works under the hood explore key Concepts like inheritance property descriptors and the difference between prototype and instance members you’ll also learn when and why to avoid extending built-in objects and how to iterate through prototype members effectively prototypical inheritance build on the previous section with a deep dive into creating and managing your own prototypical inheritance hierarchies you’ll learn how to reset Constructors call Super Constructors override methods and even Implement polymorphism by the end of the section you’ll know how and when to use inheritance in real road projects and how to enhance functionality with mixins es6 classes transition from traditional prototypes to Modern es6 classes this section covers class syntax inheritance and static methods you’ll also dive into advanced topics like using symbols and weak maps for private members hoisting and Method overwriting these are the tools that will make your JavaScript cleaner more maintainable and align with modern best practices es6 tooling Master the tools that power modern JavaScript development you’ll learn how to use modules both commonjs and es6 as well as how to optimize your workflow flow with Babble and webpack these tools will allow you to write cleaner more efficient code and ensure compatibility across different environments which is a must have for professional developers node module system get started with nodejs and understand how it enables JavaScript to run on servers you explore node.js architecture the module system and key built-in modules like path OS file system and events by the end of the section you’ll know the fundamentals of node.js required to create powerful scalable backend systems and understand how the module Raper function and event driven architecture work node package manager learn how to manage project dependencies like a pro this section covers everything from creating and managing package.json files to installing updating and Publishing packages you’ll also explore semantic versioning and best practices for working with global and local packages these skills are crucial for maintaining efficient collaborative development workflows asynchronous drop JavaScript in this section we will cover one of the most important aspects of JavaScript asynchronous programming learn the difference between synchronous and asynchronous code and how to manage async operations using callbacks promises and async await you’ll also explore patterns for handling callback how running promises in parallel and creating subtle promises this section will give you the confidence to write efficient non-blocking code for World Ro applications so how can this structure work for you each section is designed to build in the laughs creating a seamless Learning Journey that connects theoretical knowledge with practical applications whether you’re preparing for a job interview building your own mobile app or simply aiming to master JavaScript this course will help you with the tools confidence and expertise to achieve your goals level up your career with JavaScript Pro enroll today on Steven codecraft tocom and let’s take your skills to the next level in this video I’ll will guide you through the resources and material tutal that will help you get the most out of your learning experience on Steven codecraft docomo course so if I scroll down here and click Start Learning this will navigate to the course dashboard so here on the course dashboard you can see a button that says to start the video course and if we scroll down we can also see links for the course materials so let’s first click into the video course so we can see that interface so on the left we see the videos so here if I select this particular video I scroll down we can see the different sections now I’ll press play to start the video course so I’ll pause it for now and let’s look at the different options that we have so we have an option to show the subtitles we also have a settings icon where we can adjust the speed so if the video is going too fast you can always adjust it so let’s scroll ahead up here so for each video Lesson I have an active recall study section this helps mimic a technical phone screen interview and also helps you understand where you have gaps in your knowledge so play this so here I will ask a open-ended question Focus and how does it organize software designed after as it you’ll see this text that says to pause the video and answer so manually pause the video and try to answer it in your own words I’ll press play again and then I will provide a sample answer for this question the main focus of object so after you hear the answer don’t worry about memorizing it for btim it’s just to help you understand it in case you struggled with putting in your own words so after you watch the video click on the button that says complete and continue so after you do that you will see a check mark next to this video Lesson and then we’ll move on to the next video in the course so let’s go back to my courses now that you’re more familiar with the video section of the course let’s go back to the dashboard for JavaScript Pro now let’s discuss the course materials so scroll down and you see these different links so for the first link is the code for the course so this section contains the completed code for the course in a GitHub repository so this includes the finished projects and examples that will be building together these resources are designed to help you see the end goal and provide a reference for what your own code should look like as you progress you can use this code as a guide to troubleshoot and refine your own projects but remember the real learning happens when you write the code yourself there’s also another link for the starter files so these files are neatly organized into folders with clear name and conventions to match each video in the course so we’ll click into one of these folders in this case the object section and here you can see different files corresponding to each video Lesson so you can click on this green button you can either clone the project from your terminal or click on download zip and you can open that in s code there’s also an ebook in the course section and this is a 600 page comprehensive ebook and it covers all the topics that we’ll discuss in the video lessons so I strongly encourage you to read the relevant section of the ebook before watching the associated video I’ll scroll down here so you’re more familiar with what the ebook looks like so here we have the introduction and discussion of objectoriented programming So reading the material ahead of time primes your brain for what’s coming in the video making it easier to follow along and retain the information there’s one more ebook in the course materials which is the active recall study questions so this is to ensure that you solidify your knowledge and prepare for worldw applications and Technical phone screen interviews so this PDF contains all of the active recall study questions that we will go over in the videos and this is to test your understanding of key Concepts and build a solid foundation in JavaScript programming let’s scroll here so you’re more familiar it looks like so these are all the questions for section two so you go through each of these and try to answer in your own words and don’t worry about memorizing it for btim of the answer that I provide then you can scroll down so if you struggle with answering that I provide a sample answer so I highly recommend that you take the time to answer these questions even if you’re unsure about an answer the process of thinking about it and putting in your own words will strengthen your understanding and of course you can always refer back to the ebook or the video for clarification these course materials are here to support you every step of the way by engaging with them which includes the finish code the starter files the ebook and the study questions you’ll set yourself up for success and gain a deep lasting understanding of JavaScript to start programming JavaScript there are two essential tools you need to install node.js and visual studio code so what is no. JS this is a powerful runtime environment that lets you run JavaScript outside the confines of a web browser it’s what enables you to build and run JavaScript applications on your computer including server side project while you could just run JavaScript in your browser for this course you will be using node.js to execute our programs the second tool is Visual Studio code otherwise known as vs code developed by Microsoft this is an integrated development environment or IDE for short and this is where you’ll spend most of your time writing testing debugging and running your code it’s a versatile desktop application used by developers worldwide and we’ll be using it throughout this course both node.js and visual studio are free and easy to install installing node.js Begin by opening your browser and heading to nodejs.org once you’re on the side click the download node.js LTS stands for long-term support downloading this version is recommended for most users because it’s the most stable and well supported version of node.js once downloaded open the installer and follow the onscreen instructions the default settings are suitable for most users so you can proceed with them unless you have specific preferences installing Visual Studio code next we’ll install our IDE navig to code. visual studio.com in your web browser click the download button for your operating system vs code is available for Windows Mac and Linux after downloading run the installer like with nodejs the default installation options will work perfectly for our purposes so now once you have installed both nodejs and visual studio code click to open up vs code after you click it you will see the welcome page then open up finder or File Explorer for your windows and create a new folder now this will be the folder where we place our code so I’ll just name it project now the name of the folder doesn’t matter then I can click and drag it into V s code this will open up the project now to add a new file to our project I can click on this icon and I can name it code. JS so the name of this file doesn’t matter but the file extension does so now we can write our first line of code and I’ll say console.log then in single quotes I’ll say hello world and then I’ll end it with a semicolon notice as I’m typing this file has not been saved yet and so I see a circle indicating that I have unsaved changes so to save it I can do command s or on Windows it would be control s so now if I want to actually execute this file I can do file appearance and then panel to open up the integrated terminal in vs code now there’s also a shortcut I can do control and back tick so if you don’t use the back tick character often it’s located on the left hand side of your keyboard above the tab key so I can do control and back tick to toggle this open so I’ll be using node to execute this program so I’ll type node and then the name of our file which is code. JS so here we see this value hello world is log to the console so I’ll close this now vs code offers a lot of features and a lot of ways to customize it before this course we’ll just be covering the basics that you need to get started so on the left hand side is the activity bar where we see a list of icons the topmost icon is the folder icon and we can use it to toggle our project to see the folders and files within it next is the search icon and we can use this to search find and replace text so for example let’s say if I do hello enter we see that this text is found in our code. JS file so close that the next one is our source code icon and this is used to keep track of the changes in our project as well as collaborate with other developers using get ver control next is the run and debug icon you would use this when setting break points in your code and debugging it if there are errors next is the extensions icon this gives you access to the extensions Marketplace this enables you to install additional features to VSS code to improve your productivity and help you customize vs code to your needs now the icons on the bottom is for your account and to adjust your settings now on the bottom of the screen is the status bar here in Blue on the side you will see any errors or warnings in your code and on the right side I see the line number that I’m on for my current file and I also see the programming language being used so let’s say if I wanted to add another file to my project rather than always having to click on this icon I can use a keyboard shortcut of command and N or control and n on windows open up a new file and on the bottom right we see that this is identified as plain text so now if I want to save this file as a Javascript file I can do command s and I can name it as second program. JS and now in the bottom right we see that vs code can identify that this is a JavaScript file the next thing I want to cover is the command pallet you can access the command pallet by going to view and then command pallet now another way to do that is with the keyboard shortcut of command shift and P it will be control shift and P on Windows now the command pallet is very important as it is the control center for all commands in VSS code from here we can also adjust the color theme that we use so I click on color theme and as I scroll up and down we can see different color themes for my code editor you can also access additional themes we going to the very top clicking on browse additional color themes allowing you to search through different options for this course I’ll just stick to the standard Visual Studio One now to make the text larger you can do command and plus or control and plus on Windows and also command minus or control minus in order to make the text smaller so this is a quick overview of VSS code teaching you the basics that you need for this course so for this course there are two vs code extensions that I suggest and that we will be using throughout this course so click on the icon for extensions and type in Live server then you can install this extension and we’ll utilize it later in the course now this extension live server essentially makes it easy for us to have hot reloading so when we write our code we can actually see those changes reflected in a web browser then another extension that we’ll be using for the early part of this course is quoka you type in so select this one and then install it this allows us to see the output of our JavaScript without having to constantly run it in our terminal before we get started if you’re interested in supporting my courses and projects you can follow me on my new YouTube channel and Instagram at stepen codecraft you can also explore my courses at Steven codecraft tocom and if you’re looking to enhance your health and fitness routine check out my workout and meal planning app at fitfuel planner.com the app offers over 100 recipes workout plans meal plans and a grocery list feature it’s designed to make tracking your calories and macronutrients straightforward and stress free I appreciate your support and I’ll see you in the next section objectoriented programming or o op is a programming Paradigm built around the concept of objects at its core oop organizes software design around data or objects rather than focusing solely on functions and logic objects are instances of classes which serve as blueprints for creating and managing data and behavior a class can encapsulate both the data often referred to as attributes and the functions known as methods that operate on that data this combination makes it easier to group related functionality and data into a single modular structure one of the key benefits of oop is how it promotes modularity and code reusability by designing software in a way that mirrors Ro World objects and their interactions o op helps developers create systems that are easier to understand maintain and extend languages like JavaScript python Java and C are just a few examples of programming languages that support oop providing the tools to create and manipulate objects effectively oop is especially useful for managing the complexity of large software projects making it a preferred approach for many modern applications [Music] what does object orent programming focus on and how is it different from just using functions object orent programming also referred to as oop focuses on organizing code around objects which represent data and the actions that can be performed on that data this is different from just using functions where the focus is primarily on writing step-by-step instructions or logic to solve problems without grouping data and behavior together objectoriented programming or o op is a programming Paradigm that focuses on objects rather than functions this approach organizes software design by grouping related data and behavior into self-contained units called objects at the heart of oop are its four foundational principles I’ll explain each of these principles up front so you’re familiar with them as we begin throughout the course you’ll see examples that clarify these abstract ideas so these four principles include abstraction polymorphism inheritance and encapsulation first let’s discuss abstraction abstraction involves hiding the complex implementation details of an object and exposing only what’s necessary this simplifies how we work with objects allowing us to focus on their functionality without needing to understand all the intricate details behind the scenes polymorphism polymorphism means many forms and this allows objects to be treated as instances of their parent class rather than their specific class this enables methods to behave differently depending on the object that’s calling them making your code more flexible and adaptive inheritance in inheritance allows new objects or classes to take on properties and behaviors of existing ones this reduces code duplication and promotes reusability and makes it easier to maintain consistent design across your application encapsulation encapsulation combines data and the methods that manipulate it into a single self-contained unit referred to as an object by restricting direct access to this data encapsulation and ures better control security and reduces the risk of unintended interference these four principles abstraction polymorphism inheritance and encapsulation can be remembered using the acronym API transitioning from procedural programming before oop became widely adopted many programs were written using procedural programming this approach divides the program into functions that operate on variables while simple procedural programming can create significant challenges as projects grow such as code duplication and interdependencies so code duplication refers to repeatedly copying and pasting similar code across functions leading to redundancy interdependencies refers to changes in one function can inadvertently break others creating a web of interconnected issues often referred to as spaghetti code objectoriented programming addresses these issues by bundling related data and behavior into objects within an object variables are known as properties and functions are called Methods why o Matters by adopting oop principles you can write more modular maintainable and scalable code o simplifies interactions between different parts of your application reduces the risk of errors and Mak your code easier to extend and adapt to Future requirements whether you’re managing a small script or a complex system o provides the structure and Clarity needed for professional software development this lesson provided a highlevel overview of the four core principles of oop which can be remembered using the acronym API standing for abstraction polymorphism inheritance and encapsulation throughout this course we’ll explore more practical examples of of each of these foundational principles in [Music] detail what is the main focus of objectoriented programming and how does it organize software design the main focus of object or programming also referred to as oop is on objects which group related data and behavior into a single unit this helps organize software design by bundling properties and methods together making code easier to manage understand and reuse what is abstraction in oop and how does it simplify working with objects abstraction oop means hiding the complex details of how something works and only showing what is necessary it simplifies working with objects by letting you use their functionality without needing to understand all the behind the scenes implementation how does polymorphism make code more flexible and adaptable in oop polymorphism makes code more flexible and adaptable by allowing the same method or function to work in different ways depending on the object it is used with this reduces the need for repetitive code and makes it easier to handle different types of objects in a consistent way what is inheritance in oop and how does it help reduce code duplication inheritance in oop is a way for one class to use the properties and methods of another class this helps reduce code duplication by allowing you to reuse existing code in new classes instead of writing it again what does encapsulation do in oop and why is it important for control and security encapsulation and O bundles data and the methods that work on it into a single unit called an object and it restricts direct access to the data this is important for control and security because it ensures that data is only modified in controlled ways reducing errors and preventing unintended interference how does oop address the challenges of procedural programming such as code duplication and interdependencies oop addresses challenges like code duplication and interdependencies by organizing code into objects that combine data and behavior this reduces redundancy by reusing code through inheritance and makes programs easier to manage by keeping related functionality within self-contained objects reducing the risk of unintended interactions between parts of the program in JavaScript an object can be defined using curly braces which signify an object literal an object literal is a way to organize data using key value pairs so here’s you can declare an empty object so we can use the let keyword and I’ll name the object Pro programmer let’s assign this to an object literal I’ll give it a key of name and the value of my name I’ll add another key for preferred language and I’ll set that to JavaScript now I’ll Define a method which will utilize these two properties so name this write code and set that to an anonymous function so this will console.log use a template string this.name writes this. prefer language code and I’ll end it with a semicon now I’ll Define another method and I’ll use syntactic sugar for cleaner syntax so I’ll say drink coffee then open and closing parentheses then I will console log this. name drinks coffee so this shows different syntax that you can use to define methods within an object literal and I will end this with the semicolon now I can call programmer. write code control and back tick to bring up the terminal let’s navigate to where this file is so it is in objects and here I’ll do node and I name this file three object literals JS and here I see it logged these property Val vales so in this instance the programmer object literal has four members so it has two properties the name and the preferred language and has two methods write code and drink coffee so this structure allows us to encapsulate related properties and functions within a single organized entity making our code cleaner and more intuitive to work with by leveraging object literals you can create versatile and reusable code structures that represent rward entities or complex data models effectively what is an object literal and how would you create one an object literal is a data structure in JavaScript that allows you to Define key value pairs it essentially enables you to group together variables and functions in the context of an object it will be referred to as properties and methods and you would create one by using curly braces to help reinforce this concept your exercise is to create a simple JavaScript object literal representing a grocery list item this object should have the properties of quantity and name along with a method display that logs the quantity and the name to the console in this format so to demonstrate how you can implement this I can use the cons keyword and I’ll name it grocery item could assign that to an object literal with the key of name I’ll just set that to appps and the key of quantity I’ll set that to four and our method so that will be display console.log back ticks so I’ll say this. Quantity times this. name end it with the semicolon and we’ll close our object literal with a semicon then I can call grocery item. display I can just log this out and I see the expected [Music] output so suppose you need to add another programmer to your team using the object L syntax repeatedly can lead to duplicated code which makes your application harder to maintain this is especially true for objects that include methods indicating that the object has Behavior which may be repeated across multiple instances so let’s consider this object L that we created in the previous lesson if we need to create multiple programmer objects it will be inefficient and air prone to copy and duplicate all this so a more scalable solution is to use a factory function so a factory function is a function that returns a new object each time it is called ensuring that each object has its unique properties but shares the same methods so here’s you can Implement if I name it function and I want name it create programmer so now we’ll specify two parameter variables the first will be name and the second will be prefer language then we’ll return an object literal we do name prefer language we’ll do write code for the method and we can just copy this then the other method is drink coffee and once again we’ll just copy this console log statement and since it’s is a function we don’t have to end it with the semicolon so we can now create a new programmer simply by calling this function so I’ll scroll down so we can see it I’ll say const new programmer equal to create programmer pass in the name Alice and JavaScript as the preferred language so now when I call a new programmer recode let’s pull out the panel and I’ll scroll down I’ll list it out and so I’ll do node I’ll just copy the name of this file and I’ll output it and here we see Alice writes JavaScript code so using Factory functions in this way helps avoid code duplication and simplifies maintenance making your code base cleaner and more manageable [Music] what are Factory functions and why would you use [Music] them Factory functions provide an efficient way for us to create a new object so the name of the function will be in camel case notation and it can accept parameter variables these parameter variables can help customize the values of the object being returned the benefit is that it reduces code duplication and the need to copy and paste [Music] create a factory function which returns a new grocery list item the parameters should be name and quantity so this is the grocery list item which we created in the previous lesson so rather than having to duplicate this we create our Factory function so I say create grocery item and this accepts name and quantity as parameter variable this returns a new object literal it will be name quantity and for the method we can just copy this and paste it here we can end this with a semicolon and so now if we wanted to create a new item we can say h new item is equal to create grocery item we’ll say bananas end up with the S and we’ll just say five so I’ll scroll down we can call new item. display so let’s bring up the terminal and I’ll run it again and here we see the quantity of five [Music] bananas in traditional JavaScript there are no native classes as found in languages like Java or C instead JavaScript uses functions and the new keyword to mimic class life Behavior which is a technique known as Constructor functions this approach was the standard before es6 introduce class syntax as syntactic sugar to simplify object creation and inheritance we willover es6 and that syntax later in the course but for now here’s an example of a Constructor function for creating programmer objects so here I’ll just write a comment to say the lesson and we’ll start up quok so I bring up the command pallet with command shift and P or control shift and P and I will say quoka start on current file so you don’t see this just type in quok select that so now we can see it in our output without having to run node in the terminal so use the function keyword and we use Pascal case for naming our Constructor function and it accepts two parameters which is the name and the preferred language of the programmer language then I’ll use the this keyword which means this current object set it to the name then the preferred language now let’s Implement our methods so this. write code is set to the anonymous function console.log back TI for our template string and I’ll say this.name writes this. preferred language code we end this with the semicon and the anonymous function I’ll say this dot drinks coffee set that to Anonymous function console.log I’ll say this.name drinks coffee just to demonstrate the centx Now to create an instance of this object and to call this Constructor function we use the new keyword so I’ll say con new programmer equal to new programmer then we pass in our arguments I’ll pass an ALICE for the name and on JavaScript as the preferred language now I can call new programmer. write code save that and here we see the output Alice writes JavaScript [Music] code what is a Constructor function a Constructor function is used to instantiate a new object in JavaScript so for the name of convention you would name the function using Pascal case and for assigning the properties and for the methods you would use the this keyword which references this object or the current [Music] object so now for the exercise create a Constructor function for the grocery item so to implement that once again we use our function keyword and we use Pascal case so the first character of each word is capitalized this takes in two parameters the name and the quantity or this keyword with this object just assign this to the quantity now for our display method this. display set that to an anonymous function console.log back TI this. quantity times this.name end that with the semicolon so now we’ll create instance of the grocery item and we call this Constructor function with the new keyword so say const new item is equal to new grocery item for the name we’ll say bananas and the quantity of five so now let’s call this display method so that be new item. display save that and here we see the output which is five bananas every object in JavaScript includes a special property known as Constructor this property references the function that was used to create the object via the new keyword for instance we consider our Constructor function for a programmer object here we use the new keyword to call this function so if we wanted to find out which Constructor function created this object we can access that via its Constructor property so let’s console log that so I’ll say new programmer. Constructor now when we log that in the console so this file is named Constructor property. JS so this will output the programmer function confirming that new programmer is an instance of this programmer Constructor function so this property is particularly useful for confirming the type of object you’re working with especially when dealing with complex code bases that involve multiple Constructors and [Music] prototypes in JavaScript functions are treated as objects this means that like any object a function can have properties and methods and it can be assigned to variables or passed as arguments to other functions so let’s consider a simple function I just name it add and it takes in two numbers num one and num two and it simply Returns the sum of these values so you can assign this function to another variable effectively creating a reference to the original function so I ad do cons if I just name this n and assign that to add now n will reference this function as fun funs are objects in JavaScript so now can actually call that function console. log with this reference n so I can say N I can pass in two and two so I’ll expect the output of four so starting up CA I see that the output is four so as an object the function add has properties and methods for example the length property of a function returns a number of its expected arguments so I were to do console.log of add. length we get the value two as there are two parameter variables so to further illustrate how functions are objects consider creating a function using the function Constructor so I can name that with const programmer Funk equal to new function taking in the name and I’ll use back six so this.name assign to name and to find a method write code assign to an anonymous function console.log code in JavaScript so let’s instantiate an instance so I can say cons and I’ll just call this programmer is assigned to new programmer Funk and I’ll pass in my name as the argument so now let’s call this method right code programmer WR code and here we see our expected output so this lesson shows the unique nature of functions in JavaScript by understanding that functions are indeed objects you gain a deeper understanding into the flexibility and capabilities of JavaScript as a programming [Music] language so for your exercise create a function named calculate price so this function will accept two parameters a grocery item object and a price which is just a number so in that function simply return the price times the quantity of the grocery item so based on our previous lesson we created this Constructor function to create a grocery item and we instantiated a new item so we want to create the function calculate price which accepts a grocery item and a price and we simply return the price Times Grocery item quantity so we want to assign this function name to a variable to demonstrate that functions or objects in JavaScript so we do const perform calculation is assigned to calculate price so now we can invoke it with this reference so let’s do console.log perform calculation so for the first argument we’ll pass our grocery item and we’ll pass 25 cents so here we see the output in quoka is 125 JavaScript supports eight different data types which include seven primitive types and one complex type the Primitive types are are number string Boolean big int undefined null and symbol the eth data type is object which also encompasses arrays and functions understanding the distinction between these types is crucial due to how they are allocated and managed and memory so to demonstrate primitive types these are passed by value so when you work with primitive values these are passed by copy so this means if you assign a variable to another containing a primitive value the new variable gets a copy of that value so altering one will not affect the other because each variable holds its own unique value in a separate memory location so find sanche let a initialize that to the value of 10 and I initialize B and I assign that to a b will get a copy so they are not referencing the same data in memory so if I do a and I Reign that to 20 let’s start qua console log this conso loog the value of a and we’ll cons out the value of B here we see they are different values so now let’s consider reference types which are passed by reference so on the other hand reference types like objects are handled differently so they are passed by reference meaning both variables point to the same object in memory thus changes made in one variable are reflected in the other so say if I assign a and assign it to an object with the value of 20 then if I assign B to a they now reference the same object in memory so if I update a. value to be 100 this will be reflected in both of the references so let me just copy these console log statements and output them here we see they are referencing the same object so in JavaScript primitive values are copied by value meaning they do not affect one another when changed now objects which include arrays and functions are copied by reference meaning changes to One affect any other variable referencing the same object this fundamental understanding helps in managing how data is passed around round in your programs ensuring fewer surprises and more predictable code Behavior what are primitive values and what do they pass by primitive values refer to simple values such as string number booleans and they are passed by copy what are object values and what are they passed by object values refers to key value pairs this also includes arrays and they are passed by [Music] reference so objects in JavaScript are inherently Dynamic which means that you can add or modify their properties and Methods at any time after their creation using the cons keyword with an object declaration ensures that the variable cannot be reassigned to a different value however the contents of the object it points to such as its properties and methods can still be altered or extended so consider the following example find Stan a person object and I give it the key of name and the value of my name let’s end it with the semicolon Now by console log this console.log of person now let’s start up gu so bring our Command pallet start on current file here we see it just outputs our object now if we want to add properties we can do so using either dot notation or square bracket notation so if I use dot notation first I can say person. favorite food assign that to tacos and I’ll just copy this console log and we output it just to demonstrate that I have dynamically added this property and here we see this contains the two properties for the name and favorite food now let’s use the other syntax which is the square bracket syntax and I’ll call this favorite ice cream and let’s just assign that to chocolate now let’s paste our console log statement and here we see our object has been updated now we can also use the delete keyword which will delete a property so if I do delete person favorite ice cream and let’s paste this again and here we see our object has been updated dynamically again deleting the property of favorite ice cream now let’s add a method so I can say person. e let’s assign this to Anonymous function here I’ll say console.log with back ticks and I can say this. name eats this. favorite food and then with the semic so now let’s invoke this method that we’ve added dynamically so I’ll say person. save that and if I look here let me expand this we see Steven eats tacos is the output so this ability to modify objects is both powerful and flexible allowing us to adapt objects to changing requirements or conditions dynamically however it also means that you need to manage objects carefully to avoid unintended side effects from these changes explain in your own words how are objects Dynamic objects in JavaScript are dynamic because you can change and mutate the properties and methods of the object after it has been [Music] initialized so for your exercise create an object with the grocery item Constructor function then dynamically add the property of grocery a so here we have this grocery item Constructor function let’s instantiate an instance of it so we can do that with const new item call the new keyword grocery item we’ll name this bananas the quantity of five now we want to dynamically add a new property so I can say new item do grocery aisle and I’ll set this to the produce section now let’s just console log this console. log of a new item and here we see we have dynamically added the property of grocery [Music] aisle in JavaScript different Loops offer various ways to iterate over collections like arrays and objects for arrays we can use the four of loop so the four of loop is ideal for ating over array elements so if we do let numbers and I assign this to an array of 1 2 3 4 and 5 then if I just do four con element of numbers then console. log of element here we see the output is just each of these elements now for objects we can use the forend loop so the forend loop allows you to iterate over the keys of an object and this is useful for accessing values when you know the structure of the object so I can do con dog and instantiate this object with the name of Max the age of five and so the eye color of blue we’ll end this with the semicolon now we can use our 4 n Loop so four and I can say cons key in the dog object now I can do console.log of dog and access the key with square bracket notation and here I see this output the associated values for each of the keys so besides these two traditional Loops JavaScript provides methods to retrieve the keys values and key value pairs directly from objects which can be iterated over with the four of loop so let’s say if I want to get the keys I can do cons Keys equal to object. keys of the dog object so now I do const key of keys I can do console about log of key and here this will output all the keys of this object likewise I can do the same with the values so cons values equal to object. values of the doc object now for cons value of values console.log each of the values so now this outputs the associated values now we can also enumerate over the key value pairs with object. entries so I can do const entries of object. entries pass this object in now I can do four F entry of entries now here I can do console.log and I’ll use back ticks because I’m going to use interpolation the key which I can access at the first index so that be index is zero and the associated value which would be entry at the index of one so we can save this and said object is supposed to be dog as our object so here are the outputs the associated key value pairs for each of the properties in the dog object so these methods provide a powerful and flexible ways to handle objects in JavaScript they simplify the process of working with objects properties it makes your codee cleaner and more efficient how can you enumerate over the properties of an object there are different ways toate over the properties of an object one way is you can use the fourin loop to iterate over the keys of an object we can also use the built-in object class for example iterating over the keys with object. keys enumerating over the values with object. values and enumerating over the properties with object. [Music] entries so for your exercise write three for Loops enumerating over the object’s Keys the object’s values and the object’s key value entries so to complete that let’s enumerate over the object’s Keys we can do that with or I can say cons key of object. keys and for the argument I’ll pass in this object that we created then we can CL for log the key so here we get all the keys for object that we enumerate over now we can Loop over all the values so I can say cons value of object. values passing a new item and here we just console log the value so we get the associated values that we passed in as arguments when we first instantiated this object so now let’s enumerate over the key value entries so I can say for con entry of object. entries new item but now we can do console.log we’ll just log out entry so here we see each entry is an array where the value at the zeroth index is the key and the value at the first index is the associated value abstraction is a core Concept in objectoriented programming that involves hiding complex details while exposing only the necessary parts of a class or object to the user this makes the objects in our applications easier to interact with and reduces the impact of changes so let’s consider the programmer Constructor function that we’ve been using and I’ll illustrate the concept of abstraction so we use the function keyword and I use Pascal naming convention to name our Constructor function the parameters are name and preferred language so now we use the this keyword to assign our properties and we will assign our preferred language so now that we’ve assigned those properties let’s create a public method just create a comment just to illustrate that so we use the this keyword to create our public method and I’ll name it write code we assign this to an anonymous function now I’ll use a keyboard shortcut so I can just type out log and so here vs code says log to the console so I can press tab for autoc completion so now I’ll use back ticks because I want to use string interpolation so dollar sign and then curly braces this. name so I’m utilizing this property in our string wres this. prefer language code so this public method is accessible through do notation when we create an instance of this programmer so now to demonstrate a private method so the concept of abstraction refers to using private methods such that the public methods are only those that are absolutely necessary and we want to abstract away the details so I can use the cons keyword I can also use the let keyword so if you recall both the let keyword and the cons keyword are only available within the block that they are defined in right so you can only call it within the block that it’s implemented in so I assign this to an anonymous function so we’ll use our keyboard shortcut again with log and then down arrow and then tab and once again I’ll use back ticks and use interpolation so this.name drinks coffee so now let’s define another public method and now we will utilize this private method that we defined so I’ll use the this keyword and I’ll assign this to an anonymous function and here I will just call our private method so here we see with abstraction we are abstracting away the implementation details which is hidden from the user so to better illustrate this I can create an instance of this programmer so I can say cons programmer I’ll use the newy keyword which calls this Constructor function and we named it programmer so I’ll say name Steven and preferred language is Javascript so now if I do programmer dot here I can see what is accessible through do notation what its public interface is so here I see the name property I see the preferred language and I see the public methods of start day and write code so let’s call write code and I’ll just do shift option and down arrow to create a copy and I’ll try to call drink coffee so here I’m attempting to call this private method and let’s see what happens I’ll save it with command s now I’m going to bring up the terminal so I’m going to do command and J for that so here I’ve already navigated to the directory where this file is located and I name this file 11y abstraction. JS but your file could be named differently and here I’ll just run it in the terminal rather than using qua to better illustrate this so 11 abstraction. JS so here we run it if I scroll up when I called write code this outputs this. name writes preferred language code and so here we see the output is Steven writes JavaScript code so that worked as expected however here we see we try to call this private method and we get a type error that programmer. drink coffee is not a function so we know it’s not accessible and this is what will occur if we try to call a private method so it would throw an exception so now we want to instead use the public method right so only public methods are accessible through dot notation so I’ll clear this with command K and then up arrow and we’ll run it again so now I see I get the expected output when I ran right code however when I called start day this called the private method I defined where we have this. name drinks coffee and here we saw the output of undefined drinks coffee so this means that this.name is currently undefined within this context so if you remember in JavaScript functions are objects and they have their own this context so in this instance this example rather this is referring to the function that is defined in however we want that this keyword to instead reference its enclosing scope so the enclosing programmer such that we can access this. name so order to do that we can use the bind method so I can say bind and I’ll say this which references the current context that’s being implemented in so that Constructor function so now if I run it again let me clear this with command k up arrow and then run and here I see the expected result for this private method call inst start day which is Steven drinks coffee so that is the result of calling this method so to recap in this example we saw that let me close the terminal so you can actually see it right code is a public method that is accessible to any instances of this programmer Constructor function and on the other hand drink coffee is defined as a private method inside the Constructor function and here we use the cons keyword so this method is not accessible from outside this code block so outside the programmer function instead it is meant to be used internally by other methods within the programmer object like start day here which exposes a controlled interaction with drink coffee so this illustrates the concept of abst abration which is utilizing private methods and hiding away the implementation details so some key points on abstraction that I want to discuss two main points one is you just want to show what is necessary in the public interface so in our example here we see that start day that method abstracts away the details of what starting the day entails for a programmer so in this case drinking coffee now the consumer of this programmer Constructor function does not need to know the implementation details they just need to know that they can start the day and call that public method the second point of abstraction is hiding the complexity so methods like drink coffee do not need to be exposed outside of this object as they handle specific functionalities and implementation details that are not relevant to the programmer that is utilizing this Constructor function so this approach helps in maintaining a cleaner interface for the objects making them easier to use and reducing dependencies on the internal implementation details so we can always change those implementation details in the future and minimize the impact of those changes so this leads to better modularity and easier maintenance of our [Music] code so in this exercise we will build upon the grocery item Constructor function that we’ve been using in previous exercises and we will create a grocery list Constructor function so this will help us understand the concept of abstraction which involves hiding the implementation details and exposing only the necessary parts so here is the initial grocery item Constructor function so the grocery list Constructor function should internally maintain an array to store grocery items it should also provide methods to add items display all items and get the total quantity of items so to practice abstraction we will use private methods for operations that should not be exposed directly specifically you will Implement a private method for calculating the total quantity of items so here’s a starting point for the grocery list Constructor function use the function keyword we’ll name it grocery list this doesn’t accept any parameters for the Constructor function then internally we have items which will hold the grocery items I’ll just add a comment private array to store items your task is to complete the grocery list Constructor function by adding the following methods you’ll Implement add item which accepts two parameters for a name and quantity and this adds a new grocery item to the list there is display items which will display all items in the list there is get total quantity which will return the total quantity of all items and we have a private method calculate total quantity to calculate the total quantity of items so by the end of this exercise you will have a better understanding of how to implement abstraction in JavaScript using Constructor functions so now let’s Implement our grocery list Constructor function I’ll scroll down so we have more room so now first let’s Implement our private method to calculate the total quantity of items so you can use the cons keyword and on name this and we’ll name this calculate total quantity we assign this to Anonymous function now we will return this quantity and we utilize the reduce method that’s built in for the array data type so items. reduce so with this we can take all the items in our list and reduce it to one value so here we pass our callback function so the previous value which we can name that total and the current value so I’ll name that it we use our Arrow function syntax so the total plus the item do quantity right so here for our grocery list we have the properties of name and quantity now for the reduce method it also takes an optional second parameter set that to zero and this represents the initial starting value so now I’ve implemented that what a comment here just so we know that it is a private method so now we will Implement our other methods needed to operate on the grocery list array this. add item so an anonymous function picks in the name and a quantity so now let’s create that new object so cons item and then new grocery item says pass in these arguments to create the new object and then we will add it to our items array so now we Implement our display items method assign this to Anonymous function then we can do items and here we can call the buil-in for each method so it would be the item the current item that we are operating on and we simply want to call the display method so the display method we have implemented here and here this console logs the quantity and the name of the item so we can Implement all this on one line so now want to implement get total quantity set this to an anonymous function and we simply will call this private method that we have implemented here so now let’s utilize this grocery list Constructor function so I’ll say cons I’ll name it my list and we’ll use the new keyword then grocery list and this doesn’t accept any arguments so now that we’ve created a list let’s add items to it so my list. add item so I’ll say banana and a quantity of five then just to copy this I’ll do shift option and then down arrow just rename it to be apple and let say the quantity is three let me scroll down so you can see so now let’s call my list do display items so this will go through an output so let’s bring up the terminal so command and J or control and back tick so I’ll do up eror and then I’ll run it so here I see when I call display items this outputs the quantity and the item name for all the items in our list so now I’ll comment this out and I’ll close the terminal just so we can see better now I want to console log I’ll use back tick now I want to find the total quantity of items in our grocery list so total quantity we use interpolation here so my list do get total quantity so we’re calling that public method end it with the semicolon so once again we’ll open up the integrated terminal so command and J or control and J up arrow and we’ll run it again and here we see the total quantity is eight items in our grocery list so some key points on abstraction once again we want to show only what is necessary so only the methods of add item display items and get total quantity are exposed to the user the user does not need to know about how the total quantity is calculated so that is a private method and the second key point is hiding the complexity so if I scroll up again so the calculated total quantity method is private and its functionality is the internal implementation details that should not be exposed closures in JavaScript are a powerful way to achieve encapsulation which is one of the core principles of object ored programming so if you remember our acronym of the four pillars of object programming which is a pi so the A is for abstraction the P is for polymorphism the I is for inheritance and the E is for encapsulation so what is a closure a closure means that an inner function has access to variables declared in its outer function this allows you to hide the internal State and functional of an object exposing only what is necessary to the outside world so this is a technique that enables us to achieve encapsulation so using closures we can create private properties and private methods making JavaScript objects easier to work with so instead of overwhelming the user object with too many public properties and methods you only expose what is absolutely necessary for the object to function properly so let’s go over a simple example to better understand the concept of closures so I use the function keyword and and I’ll name this function example So within it I’ll create a constant named num and I will initialize it to the value of five so now I’m going to create a function within this function so remember in JavaScript functions are objects so I can name this log [Music] num and here I’ll type log and then I can log to the console so I get that auto completion that Visual Studio code provides for me now log out that identifier of num so now I will call or invoke log num so now let’s call example so here we see this inner function has access to the variables declared in its outer scope so it’s outer function which is this constant value so let me bring up the integrated terminal I’ll do that with command J you do this with control J so node and I name this file 12 hyphen private do tab so Auto completes for me so we output that so here when we invoked call this function example we get the expected output of five this is a simple example demonstrating the concept of closures where inner functions have access to variables declared in its outer scope so let’s go through a more complex example in the case when we we return the function so rather than simply defining this function or declaring it rather let’s instead return it so can do return and we’ll delete this so now this function returns a function and so when we call example we want to store the result I’ll name this inner function initialize to that and so now log num is now accessible through inner function right so this is referencing the function that is being returned so now let’s call that inner function in function and we invoke it let’s bring up the integrated terminal again up arrow and we’re running and once again we get the expected result so even though this function which we named example has finished executing inner function still has access to num because of the closure so even after this example or even after the outer function has finished executing the inner function is still able to access all the variables and identifiers declared in its parent scope at the time of Declaration right so you’ll get more practice with this and you’ll become more understandable let’s go over a more complex example and here we will create private properties and methods using closures within a Constructor function

so once again we use the function keyword and I’ll just name this make functions so here if we use the let keyword I’ll name this private num I’ll initialize it to the value of zero so now we’ll create inner function function private increment so this increments the value plus plus so now we have these local values which are not accessible outside of this function and here we will return a JavaScript object and we will define an interface right so methods to use so we’ll have our log num method we’ll Define this with an arrow function so we’ll do log and then tab for that autoc completion this will console log the number now we’ll Define another method increment once again we’ll use an arrow function to Define it curly braces so this will call Private increment here we do log Tab and we’ll just say increment it so now let’s call make function I’ll say cons now we can destructure these values so use curly braces log num and increment make functions and so this is an example of destructuring so we know make functions returns an object and we’ve D structured these two methods so now it’s easier to work with now if we didn’t do destructuring we could name this for example increment object we could really name it anything and through increment object we can access the increment and lognum methods but I prefer the destructuring syntax so did command Z to get back to that so now let’s call log num this will output the value of zero which it was initialize with then we can call increment which will update the value and we will see the console log value of incremented and then we can call log num again so let’s bring up integrated terminal again here I will scroll down we’ll clear it with command K up arrow and we run it again so here we see the initial value of private num is zero we incremented the value and the updated value is one so this shows an example of closures as this make functions has finished executing but here this JavaScript object and the methods defined within it still have access to these identifiers or the the variable is declared in its parent scope and this helped us achieve encapsulation because we only expose log num and the increment method and we’re not exposing the in implementation details or the private num property so let’s clear this out we’ll go through another example so using closures in a Constructor function so we’ll go back and we’ll use our example for the programmer Constructor function the parameters are name and preferred language so I’ll just write some comments just so it’s easy for us to identify what we’re doing so we’ll specify a private property so we’re not going to use the this keyword so it’s not accessible through do notation so I’ll use the let keyword instead and we’ll assign this to the value of name now an example of a public property which will be accessible through notation so this do preferred language assign to that parameter of preferred language so now let’s define a public method we use the this keyword say write code assign this to an anonymous function let’s do log and then tab for the auto completion we use back ticks and we can say code in this preferred language now an example of our private method Again Play Let drink coffee assign to an anonymous function here we will log it again so log to console I’ll just say gulp dot dot dot now we’ll say a public method that uses a closure so this. start day assign this to Anonymous function and we just call drink coffee so we are hiding those implementation details of this so let’s actually instantiate a new programmer so we’ll say const programmer we use the new keyword and the name of our Constructor function we’s say Alis and the language is Javascript and this with the semic colum now programmer. write code and we’ll say programmer. start day right so this repetition is really good to help you get used to the syntax as well as get a better understanding of the terminology that we use in programming let’s scroll down open up the integrated terminal up arrow and run so here we see code and JavaScript and go so in these examples let’s close this and we’ll look over our implementation of this Constructor function so private name let’s actually use it so can use private name right so let’s run it again to make sure that we’re actually utilizing our private property so here we see Alis codes in JavaScript and just sculp so private name and drink coffee are private because they are defined with the let keyword and not exposed via the this keyword so considering public properties and methods preferred language and write code are public because they are defined with the dis keyword and can be accessed outside the function and through dot notation once we create an instance of this Constructor functions programmer so using closures so the start Bay method demonstrates a closure is a public method that can access the private drink coffee method because of the closure it can access uh variables and identifiers is declared in its outer scope so let’s consider closures versus scope so scope is the context in which variables and expressions are visible or can be referenced if a variable is not in the current scope it is unavailable for use now for closures these are functions that capture and reference external variables so when I say external variables this refers to variables which are not defined locally in the function but these variables are accessible because they exist in the outer environment the function defined in the closure remembers the environment in which it was created at the time of function declaration this is why drink coffee this method remains accessible only within functions defined in the same scope so only within the Constructor function so closures are a fundamental and Powerful aspect of JavaScript allowing for more secure and modular code by protecting and encapsulating behavior within objects so we’ covered a lot of new terminology in this lesson I’m not expecting you to remember and nor all of it immediately and we’re going to get more practice and more exposure to these Concepts throughout the course so it will make more sense the main takeaway that I want you to get from this lesson is that a closure means that inner function has access to variables declared in its outer function what are closures so closures are inner functions that are able to access variables defined in its outer function so in other words closure functions can access variables from their outer scope even after the outer function has finished executing now you would utilize closures in order to achieve encapsulation and to hide private variables or private properties so now for your exercise the objective is for you to understand and Implement closures to create private properties and methods within a Constructor function so your task is to create a bank account Constructor function that can manage a user’s account balance so the balance should be private and the Constructor should provide public methods to deposit money withdraw money and check the balance so now to go over the instructions step one you want to define the bank account Constructor function now it should have a private variable balance to store the account balance it should have a private method to validate the amount being deposited or withdrawn so this private method will validate and ensure that the value that you’re passing as an argument is of the number data type and that the amount stored in the balance is greater than the amount being withdrawn as well as the money that you’re depositing is a positive number so it should have public methods to deposit money withdraw money and check the balance so step two you want to implement the following public methods the first is deposit which accepts the parameter of the amount to deposit so this adds the specified amount to the balance if it is valid right you’re utilizing that private method to validate the argument the second method or second public method is withdraw which accepts the parameter of the amount and this subtracts the specified amount from the balance if it’s valid and there are sufficient funds now the third public method is get balance which simply Returns the current balance so pause the video and attempt to implement this Constructor function for the bank account so now you’ve attempted to implement that we’ll go ahead and write the code for that so we use the function keyword then name of it is bank account now for the parameter I’ll specify initial balance now I’ll use this as a private property so it’s not accessible through notation you can only access it through the public interface or the public methods this helps us achieve encapsulation so we’re setting that to the initial balance and I’ll add a variable just to better describe what I’m doing so private variable to store balance okay now I want to implement the private method to validate the amount so this amount could be what is being used to either deposit money or to withdraw money so cons I’ll say is valid amount the anonymous function parameter being amount so return and I’ll use the type of operator CU I want to ensure that the amount is of the number data type so and we will check that the amount is greater than zero because we can’t deposit a negative number and we don’t want to withdraw a negative number so we can utilize this helper method in our public methods that we’re going to implement so I’ll just say public method to deposit money so we use the this keyword to create a public method within our Constructor function we name a deposit and we assign this to an anonymous function with the amount being the parameter now we’re going to use utilize our private method so if is valid amount for the amount then I’ll do curly braces so in the case when the amount being deposited is a number data type and is a positive number then we want to perform that update so we’ll use our shorthand syntax to update the balance in the bank account and we will log it out so I’ll say log down arrow and then tab I’ll use back ticks so deposited now the colon now we’re using interpolation so I’ll do a dollar sign and the curly braces and the amount now because I’m doing US dollars I want to use the dollar sign in the actual output so I’m going to add another dollar sign before just so um the correct symbol shows up when we output it to the console so now else in the case when it’s not a valid amount so do log then tab and and then I’ll say invalid deposit amount so I’m informing the user on that so we’ implemented this I can end that with the semicon now want to implement the public method I’ll scroll up so you can actually see better so public method to withdraw money so now we’ll do this do withdraw we assign this to an anonymous function now once again um we’re utilizing our helper method so if is valid amount we ensuring that that is a number data type and a positive number and if the amount that we’re trying to withdraw is less than equal to the balance then we can actually perform that so we use shorthand syntax to update the balance so minus equals and we will log that to the user to inform that this has been successfully performed back ticks with Drew interpolation the amount and we want the dollar sign show up so we’ll add that there else we’ll log and then tab insufficient FS now in the case when it is not a valid amount so in the case when the amount that you passed as an argument is either not the number not of the number data type or is a negative value then we want to Output a message for that case so I’ll say invalid withdraw amount okay so we implemented that we have one more public method which is to get the current balance so once again we use this keyword get balance Anonymous function and then we will simply return the balance so we’re just returning this private property that we set here so now we’ve implemented this I’ll scroll up so we can actually utilize it so now let’s instantiate an instance of this and call this Constructor function so I use the con keyword I’ll name the identifier my account and we assign this to new bank account now for the initial value I’ll specify 100 as the initial balance so now I can do my account. deposit not deposit 50 now let’s do my account. withdraw and I’ll withdraw 30 and we going do console.log and I’ll say my account. getet balance so let’s call it so now let’s open up our integrated terminal I could do that with command and J or control andj now I’ll do up arrow and I’ll run this so here we see the correct console logging where we deposited $50 and then we withdrew $3 and because we started with the initial balance of 100 we get the expected output of 120 so let’s close this integrated terminal and scroll back to the code that we wrote for this exercise so an explanation of it we have private properties and private methods here our private property of the balance of the bank account and the private method which is the is valid amount helper method so the balance variable and the is valid amount function are private because they are not exposed via the this keyword right we’re using the let keyword and the cons keyword so these are accessible within the block that it is defined in so accessible within the Constructor function now we have public methods with deposit withdraw and get balance and they’re accessible and public methods because they utilize the this keyword they could be accessed outside of the function through dot notation now for using closures the public methods demonstrate closures in the sense that they can access the private balance variable and the is valid amount function because they are defined within the same scope right so closures are inner functions that can access identifiers or variables in its outer function so some key points on closures first is it helps us achieve encapsulation where we hide internal State and functionality exposing only what is necessary another key point is scope so this is the context in which variables and expressions are visible or can be referenced and to recap on closures these are functions that can access variables from their outer scope even after the outer function has finished executing so by completing an attempting exercise you have more experience with closures and have a better understanding of how to create private properties and method methods to encapsulate the internal State and functionality of objects Getters and sets are special methods that provide you with a way to get and set the properties of an object this encapsulation technique allows you to control how important values are accessed and modified in your objects it’s often used to ensure that data encapsulation and validation rules are followed here’s how you can incorporate Getters and Setters into the programmer Constructor function using object define properties so here we have this private property private name and we cannot access it through do notation so in order to access that value you can do object. define properties now if I hover my mouse over that the first parameter is the object where we want to add or modify properties so I’ll use the this keyword which means this current object or this programmer object and for the second parameter I will specify an object again this with a semicolon and here we’ll Define the name of the property so name it name and then def find an object and here we can use the special keyword for get and we’ll set it to an anonymous function and this will simply return the private name so now if I actually want to use this property I’ve instantiated programmer object and do log tab I can say programmer. name so rather than having to call doget I simply can access it through a property and that will call the get method let’s run this in the integrated terminal so command J or control J and I name this file 13 Getters and Setters so do tab the auto complete and then I’ll run it and here I get the name of the programmer which I have access through that get method that we defined right through that name property which we defined here now we can also set the value we use the keyword for set and we’ll set this to an anonymous function the parameter will be the new name that we wanted to set now with Setters we can Implement validation rules to ensure that the value that we are setting is appropriate so I can check and make sure that the new name is not falsy which means that the new name is not an empty string null so in the case when value that I was setting is falsy I can log to the console and I can say the name cannot be empty and then we will use the return keyword to stop the execution otherwise we will set the private name so here say new name now let’s utilize this Setter method now we would do this through the name property I scroll down here if I want to set the name I can say programmer. name and I’ll set it to my name Steven now here I’ll copy this and here we see the name is changed so open up the integrated terminal again up arrow and we run it so here we see I successfully changed the name to be Steven we’re able to accomplish this because of the setter method now let’s check and make sure that our validation rules apply so let’s say instead of assigning this to my name Steven let’s say if it was an empty string integrated terminal clear this out and run it again here we see this console log statement saying the name cannot be empty and then when we log the name again we see it continues to be Alice which means that our validation rules were applied Getters and Setters the name property has a getter and Setter defined and the getter simply Returns the current value of the private name this private property while the setter allows you to validate the new name before signing it to private name so this is an example of encapsulation utilizing gets of Setters also known as accessors and mutators and this structure ensures that the internal St of the object in this case the private name can only be changed in controlled ways increasing data integrity and interaction safety using Getters and Setters not only encapsulates the internal state but also allows for additional logic to be implemented when getting or setting a property such as validation or logging which enhances the functionality and robustness of your code in this section we covered the fundamentals of objectoriented programming beginning with a definition of oop and an exploration of its four core pillars we covered essential Concepts and techniques including object literals Factory functions and Constructor functions which are foundational in understanding how objects are created and utilized in JavaScript we also discuss the Constructor property which links an object back to its Constructor function and examine how functions themselves can be treated as objects in JavaScript this leads to a deeper understanding of javascript’s flexible approach to oop important distinctions between value and reference types were highlighted clarifying how JavaScript handles data storage and manipulation which is crucial for Effective memory management and performance further we explore Dynamic aspects of objects such as adding removing and enumerating properties providing practical skills for manipulating object properties in real time the concept of abstraction was introduced along with practical implementations of private properties and methods which enhance encapsulation and data hiding in JavaScript finally use of Getters and Setters were discussed illustrating how these can be employed to control access to an object’s properties ensuring data integrity and [Music] encapsulation this section focuses on inheritance a fundamental Concept in object ored programming that allows one object to inherit the properties and methods of another this mechanism is key for reusing code efficiently and effectively I’ll introduce some terms that are critical to understanding different aspects of inheritance so the terms to First consider are Base Class super class and parent class so these are all synonymous and they all mean the same thing and these terms refer to the class whose features are inherited by other classes so now consider the terms derive class subass and child class so these three terms are all synonymous as well and these are classes that inherit properties and methods from the base class this relationship is often referred to as an is a relationship indicating that the derived class is a specialized form of the base class so I don’t expect you to memorize these right away I wanted to expose you to these terms so you understand what they are and we’ll see practical examples throughout this course so we can also differentiate between two types of inheritance the first being classical inheritance so this is found in class-based languages where inheritance is defined through classes and these include program languages like C or Java now the second type of inheritance is prototypical inheritance this is specific to JavaScript and this type of inheritance does not involve classes instead JavaScript uses prototypes this refers to objects that other objects can inherit properties and methods from it’s important to note that in JavaScript the traditional concept of classes is implemented differently while es6 which stands for modern JavaScript introduce class syntax it is syntactic sugar over JavaScript existing prototypical inheritance model understanding this helps clarify how JavaScript handles inheritance and sets the stage for using these Concepts to structure and reuse code [Music] effectively what is inheritance and why is it important inheritance is a concept in programming where one object can inherit properties and methods from from another object in JavaScript this is done through prototypical inheritance also called prototypal inheritance it’s important because it allows for code reuse making programs more efficient and easier to manage inheritance is one of the four pillars of objectoriented programming along with encapsulation abstraction and polymorphism what type of inheritance model does JavaScript use prototypical inheritance or classical inheritance JavaScript uses the prototypical inheritance model this means objects can inherit properties and methods directly from other objects rather than from classes as in classical inheritance what do these three terms refer to Base Class super class and parent class in JavaScript the term is Base Class super class and parent class all refer to the same concept the class from which another class inherits properties and methods these terms are often used interchangeably to describe the original class that provides functionality to a derived or child class what do these three terms refer to derived class subass and child class in JavaScript the terms derive class subclass and CH class all refer to the same concept a class that inherits properties and methods from another class with that other class being the parent class these terms are often used interchangeably to describe the new class that extends the functionality of the original [Music] class in programming enhancing an object’s functionality is a common task ask I will initialize some objects I’ll say let user and assign this so it’s just an empty object literal then I’ll create admin and I’ll create a guest so now consider these three objects that we’ve created now if we were to add properties and methods to this user object literal and we also have the admin and guest objects it is beneficial to reuse what we have in the user object as they’re going to have the same properties and methods now the admin and guest objects are more specific versions of the user object now both the admin and guest are users of the website so we can utilize prototypal inheritance to accomplish this in JavaScript objects possess a special hidden property prototype that is either null or references another object this reference object is also called a prototype when you see the term prototype think of it as interchangeable with parent similar to a parent class from which properties and methods are inherited so I’ll add some properties and methods to this user object to demonstrate this if this user object were to have the property of name I’ll set that to my name then the property of surname so I’ll set it to my last name email which is stepen Stephen codec craft.com is active say true now I can find some Getters and Setters so I’ll use the set keyword and I’ll set it to be full name the parameter will be value so now we’ll perform destructuring so I’ll use square brackets and I’ll say this.name and this. surname assigned to Value dos split on whitespace so with the set keyword I’ll be able to use full name through notation and assign it to value so for example it would look like user. full name is assigned to let’s just say Bruce Wayne for example so here is how we would utilize the setter now we call the split method on the value that is passed in which is this string and we split it on whites space so now we are destructuring it because when we call split this stores these strings into an array so Bruce would be at the zeroth index and Wayne would be at the first index and so that is how we set it here and this is a clean syntactic sugar that we can use to do it all on one line so now we Define a getter so I’ll say get full name and then I can show us return I’ll use back ticks so I can use interpolation this. name space this do surname and I’ll end this with semicon so I need add a comma here and then a comma after this so now I’ll add two more methods for log in and log out so I can console.log I’ll use a short hand so log and then back tick this. full name right so I’m using the setter here logged in then another comma and then log out to log turn then tab back to this. full name log down so here we see we have implemented properties the Setters and getter and two methods now this same functionality is also required in the admin object and the guest object now we don’t want to duplicate our code and have to copy and paste it so there is a cleaner way that we can do this utilizing inheritance and specifically prototypical inheritance or prototypal inheritance so here rather than having to copy and paste it because admin is a user of the website it satisfies that condition we can use a special property known as Proto which stands for Prototype so it’s two underscores then Proto two more underscores that will be the key for this property and we set this to user so what we’re doing here is we’re saying that the parent of this object is the user object so it’s going to inherit these properties and methods so this enables us to inherit all this functionality without having to duplicate all the code so because admin is a more specific version it is a derived class it’s more specialized than the user object it’s more specific so I can say is admin is true so here we are inheriting all the functionality of that user object and we are also extending it so I can also add a custom method manage users which is just specific to the admin object so here I would do log and then tab back ticks so here we can utilize what we inherited from the user object so this. full name is managing users now we can also utilize prototypical or prototypal inheritance in the guest object so once again we use Proto and the user so we can say is guest it’s true and I’ll add a custom method here so say browse content log and I’ll say this. full name his browsing conare notice how we are not duplicating properties and methods in our objects if you attempt to use a property not Define an object JavaScript automatically retrieves it from the Prototype this concept is known as prototypal inheritance the Prototype property is internal and hidden but it can be set in various ways one of which is using the special Proto property that we were using here so if we didn’t set it in the definition of this object literal let’s say if I were to remove this for example then we can also set it through dot notation so I can do admin Proto sign it a user so that would work as well so I’m going to do command Z undo this so if the user object here has many useful properties and methods they become automatically available in their derived objects so admin and in guest and these properties that inherits is known as inherited properties so the Prototype chain can extend even further so let’s say if we had a even more specialized object let me Define that here I can say let super admin which is an even more specific object with enhanced Privileges and enhanced functionality I can say the Proto right so it’s parent object is admin so it’s referencing as a parent this admin object and this prototype is set to the user object so super admin will inherit all of the properties and methods defined here in the user object and it will inherit the properties and the method of the admin object so let’s add some more specialized functionality I can say is super admin is true and I’ll add a method I’ll say manage admins I’ll do log and then tab this. full name is managing admit full so there are some limitations to prototypical or prototypal inheritance the first being is that prototype references cannot form a circular chain otherwise JavaScript throws an error for example setting the user Proto object to be super admin would cause a circular reference now the second limitation is that the Proto value can only be an object or null other types are IGN Ed an object may not inherit from two other objects simultaneously the value of the this keyword in methods refers to the current object even if the method is inherited so here we’re using the this keyword it’s referring to this current object the admin it’s not referring to the user object so setting a property in an inherited object modifies only that object State and does not affect the base object state so to demonstrate that by scroll down here let’s say if I already do admin. full name and I set this to Bruce Wayne now say if I log this out I will log the admin. name and I will log out the user. full name I’ll bring up the integrated terminal I go back and I change into prototypes directory I’ll do node two I’ll do tab to autocomplete it if I run it here I see the admin’s name is Bruce Wayne and by setting it it did not change its parent it did not change its prototype right so it only affected the current object so when I log out user it logs out Steven Garcia which is the value that we set when we first created the object literal so now consider the four in Loop so we can use the for in Loop to iterate over both the object’s explicitly implemented properties and inherited properties of an object so here if I just comment this out I will say for let key in admin I can do log and here I would just log out the key once again when we bring up the integrated terminal I’ll clear this command K up arrow and run it so here we see is admin we scroll to the admin implementation here we see that property being defined we see manage users which is that specialized method we implemented and we see all of the properties and methods implemented by its parent by its prototype in the user object now one thing to differentiate here we comment this out if we were to do or utilize object. Keys object. values or object. entries this will return only the explicitly implemented properties for that object it will not output the inherited Properties or methods so far to do log and then I do object. keys of the admin let’s bring up the integrated terminal up Arrow run it so here we see is admin that property that we explicitly Define and that specialized method manage users so this will not output any of the inherited properties and methods of the Prototype so for this video we were using the Proto property which is a geter in Setter for the internal prototype property however in modern JavaScript we prefer to use object. getet prototype of and object. set prototype of so a summary of what we’ covered so far in JavaScript all objects have a hidden prototype property that is either another object or null if an object or method is not found in an object Java scpt looks for it in the Prototype write and delete operations directly affect the object itself and not the Prototype so by changing that in the derived class it will not impact the parent object so by changing that in the derived object it will not impact the parent object and the Forin Loop iterates both over explicitly defined properties and inherited properties of an object while other key value getting methods only operate on the object itself so let’s go over another example in JavaScript we know that inheritance is achieved using prototypes which are essentially objects that other objects can use as a template and we know that this process is called prototypal inheritance so for another example let’s create an object that encapsulates common behavior and properties that are shared amongst all programmers so I’ll use the cons keyword and I’ll name it programmer prototype so be object literal will Define a method so an anonymous function will log it back tick say writing code in this dot preferred language comma will to find another method drink coffee s Anonymous function and we will log drinking coffee now we end this object literal with a semicolon so now we can create a Constructor function in then we’ll use this base object as its prototype so as the parent object so we’ll use the function keyword and we’ll name it programmer the two parameters are the name and the preferred language so say let private name is assigned the name so this is a private property so I can say object. define properties the first argument will be this for the current object and we’ll pass an object as the second argument so we’ll specify the property to be Nam and it will have a getter and Setter so Define the get Anonymous function and this just Returns the private name comma then set the new name private name is assigned to the new name now we’ll also set the preferred language let’s just do that here this do preferred language is set to the preferred language now at the bottom we want to inherit the common Behavior you scroll up defined in the parent object so I can say object dot set prototype of so the first argument will be this for the current object and the second argument will be the object which will be the Prototype so this case is the programmer prototype so let’s instantiate this I’ll say cons and JS programmer equal to new programmer so the name will be Alice and the preferred language is Javascript so to better explain what we just implemented we Define a programmer Constructor function that has a private property named private name we Define Getters and Setters so we can access this private name do the property of name so this demonstrates encapsulation so we are hiding the inner details of this object and we also set the Prototype with the method set prototype of so this will allow all instances of programmer to utilize the methods built into its parent object so all instances when we call a programmer we have the right code method and the drink coffee method so now let’s verify that the inheritance is working correctly by calling the methods on this JS programmer object so we can do JS programmer. write code you can try JS programmer. drink coffee now we’ll log it out so be JS programmer logging out the name so here we are utilizing this getter to get the private name now we’ll use the setter and I’ll set this to my name Steven and we will log out the updated value so JS programmer. name so let’s scroll up and open up the integrated terminal with command J so up arrow and we run it so here we see the result of the write code method says writing code in JavaScript if I scroll up this functionality is in the Prototype here we see right code in preferred language now when we called the drink coffee method this outputed the expected string drinking coffee now if I scroll back down we outputed the name so we got Alice we updated the name and log that out and we saw the name of Steven so this example showcases how to effectively use prototypes to implement inheritance and Java Script allowing for shared behavior and properties while maintaining encapsulation of private data so so by leveraging prototypes the programmer object can be extended to create various types of programmers with minimal code [Music] duplication what is the Proto property in JavaScript the protor property is a reference to the Prototype of an object it allows objects to inherit properties and methods from another object this property is used to set for access the Prototype directly but it is considered outdated instead modern JavaScript uses object. get prototype of and object. set prototype of for these tasks in JavaScript multi-level inheritance allows objects to inherit properties and methods from multiple levels of prototypes so consider this simple example if I just declare an array and I assign this to an empty array so when my array is created it is not just an instance of an array but also part of a larger inheritance hierarchy so my array is an instance of array and array. prototype also referred to as array base provides methods and properties common to all arrays now object. prototype also referred to as object base is the prototype for array base it provides methods and properties that are inherited by all objects in JavaScript including arrays this setup forms a multi-level inheritance chain where my array inherits from array. prototype and array. prototype inherits from object. prototype this is how the inheritance looks in a structured form so the base is object. prototype also known as object base then array. prototype extends that also known as array base and then our instance of the my array so some key points objects created by a specific Constructor like array will share the same prototype in this case array. prototype this multi-level inheritance allows objects like my array to access properties and methods defined in object. Prototype giving JavaScript its Dynamic and flexible nature understanding this inheritance structure helps in recognizing how methods like two string or has owned property are available to your array even though they are not directly defined within the array Constructor or on the array instance itself this concept is fundamental to mastering javascripts prototype based inheritance and helps in designing more efficient and robust applications [Music] so moving forward in this course we’ll be using the live server extension in vs code in order to improve our productivity and reduce our need to run our code in the integrated terminal so click on the icon for the extensions Marketplace and search for live server Swiss extension allows us to have hot reloading where it will run our JavaScript code in a web browser and when we make a change in our JavaScript code it will automatically update and we can see those changes without having to constantly run it in the terminal so now that you have that installed I’ll close this back to our folders I’ll create a directory so you can click on this icon and I’ll name it underscore practice you can name it whichever you prefer now within it I’ll create a new file and I’ll name it index.html now I’ll be creating a course on HTML and CSS so no need to be an expert in those Technologies we just need this file in order to open up a web page with live server also create a file named index.js and here we will place our jscript code for our lessons so back to the HTML file we need to create the Border plate for an HTML document so visual studio code will generate this for us simply type in an exclamation point and here we see emit abbreviation so just do Tab and here vs code generate this for us so now we want to reference our Javascript file so within the body element or body tags type in script and then type text SL JavaScript now we will reference our index.js file here so we’ll do source. SL index.js as it’s in the same directory then we will have a closing tag and that’s it so now now we’ll open up our Command pallet so that’s command shift and P or control shift and P type in Live server open with live server so this will open our index.html in our web browser now because we don’t have any HTML written between the body it’s just a blank web page for now so let me close the sidebar with command B and I will resize this so now our JavaScript will be running in the JavaScript console we can see that in the dev tools also I suggest that you use Google Chrome unless you are more comfortable with Microsoft Edge or Firefox so now to open up the Google Dev tools the keyboard shortcut is command option and J you can also right click and then click on inspect so here in order to get this to open in a new window click on these three dots and here when it says doc side you want to click the left most icon so this will open the dev Tools in its own window now to see our JavaScript code you want to click on console so now we can click on this settings icon to hide that now in order to see and execute our javascri code Type in log right and then we’ll do Tab and then hello world then save it and now we see it reflected on the right side console so we no longer have to constantly run it in integrated terminal so here I’ll do command and plus so we can see the text more easily so in JavaScript we know that we can define an object like this by creating an object literal say the name and the value of Steven we can end this with a semicolon and we can log out this object with person and here we see output it on the right hand console now let’s iterate through this using a Forin Loop so I can do four let key in person then log and tab and just log out that key Val value so here we see the key of name was outputed now notice how only the properties defined directly in this person object are displayed similarly if we use object. keys so let’s log that out object. keys and then the person object we output that we see the value of name so this only shows the properties defined at the object’s own level so the properties that inherited from object. prototype also refer to to as object. base aren’t displayed because of specific attributes attached to those properties so these attributes can control whether properties are innumerable rable and configurable so in other words these attributes determine whether the property will be outputed when iterating over it such as with a for end Loop or if using object. keys object. values or object. entries so let’s see this in action I’ll clear this out and we’ll examine the prop descriptor for the two string method which this person object inherits from object base so I’ll clear this out as well and I will expand this so we can see it more easily so we’ll say let object base assigned to object. getet prototype of the person object so we’re getting the parent object of this person object now we will do property descriptor this is object. getet own property descriptor of the object base so that parent object and the two string method which is defined in its parent so now we’ll do log tab property descriptor and we will see those attributes that determine whether the two string method will be shown when we enumerate through person object so let’s save this and we’ll see the result in our console let’s expand this so we see the attributes of configurable inumerable what the value is and writable so the one we are concerned about is the innumerable and we see the value set to false so when the innumerable attribute is set to false this prevents the two string method from appearing in the output of a for in Loop and methods like object. keys so you can also Define or modify these attributes so configurable inumerable and writable for properties in our own objects so for instance if we wanted to make the name property here non- enumerable you could do this so we can do object. Define property now the name of the object and the name of the property and we can pass it an object we can Define these attributes so we can say writable is false now innumerable is false so now it won’t show up when we do a for in Loop and configurable is true so let’s comment this out for now we’ll expand this so after this change the name property will no longer appear in a 4N Loop or object. keys so let’s just demonstrate that let key in the person object then we can log all the keys that are innumerable let me resize this and we can clear this out by clicking this icon you can save it and here we see there are no innumerable keys so no innumerable properties in this person object because we Define this here for the name property so by default when properties are created directly on an object they are writable inumerable and configurable attributes are set to true this allows properties to be modified enumerated and reconfigured unless explicitly changed understanding these property attributes and their implications helps in managing how data and objects is accessed and manipulated providing greater control over object behavior in JavaScript [Music] applications what are the property descriptors or attributes in JavaScript that determine whether a property can be accessed modified or iterated over in JavaScript property descriptors or attributes that determine whether a property can be accessed modified or iterated over are innumerable writable and configurable so for inumerable if true the property will appear during four in loops and object. keys for writable if true the property’s value can be changed for configurable if true the property descript can be changed and the property can be [Music] deleted in JavaScript every object has a prototype except for the root object which is at the top of the Prototype chain the Prototype acts as a template or parent from which the object inherits methods and properties accessing an object’s prototype the recommended method to get the Prototype of an object is by using object. getet prototype of this function Returns the Prototype or the parent of the specified object Constructors and their prototypes in JavaScript Constructors are special functions used to create instances of objects since functions in JavaScript are objects themselves they too have properties one of which is the Prototype property this property is not the Prototype of the Constructor itself but rather the object that will be used as the Prototype for all instances created with that Constructor so for example if I create a Constructor function with the function keyword and if I name it circle now the code within the code block so that will be used for instantiating a new Circle object so now if I log this out we know that functions are objects in JavaScript so I can do Circle and it has a property of prototype so if we log that out here we see this empty object we can expand it this object is used as the parent for all objects created with new Circle close this out and I can comment this out creating objects and their prototype links when you create a new object its prototype or its parent is set to the Prototype of its Constructor function so this is Illustrated with say if I create an object literal and I assign this to curly braces so this is syntactic sugar for let object equal to new object so the Prototype of obj or object can be referred to using using the Proto property which is an accessor property that exposes the internal prototype linkage so we’ll just log that out log and then tab see the object and then two underscores before and after Proto so here we outputed that we can expand it so this would be the same as doing say if we do log object. prototype so we get the same output close this me expand it so now if we were to expand it we can expand the get and here we see the internal prototype is object so understanding how prototypes and Constructors work in JavaScript is crucial for effectively leveraging languages object oriented capabilities by grasping these Concepts developers can better manage and utilize object inheritance in their programs and reduce code [Music] duplication does every object have a prototype in other words does every object have a parent object every object has a prototype or a parent object except for the root object which is at the top of the Prototype chain so an object will inherit the properties of methods from its prototype or parent object do Constructor functions have their own prototype yes Constructor functions have their own prototype in JavaScript functions are objects so they have their own prototype property which is used to assign properties and methods to instances created by the Constructor function optimizing memory usage with prototypes in JavaScript in Practical applications especially those involving numerous object instances it’s important to manage memory efficiently if each object instance were to maintain its own copies of methods this would lead to significant memory overhead when dealing with thousands of objects how JavaScript handles method access to address this JavaScript utilizes prototype based inheritance when a method is called an object the JavaScript engine first checks if the method exists on the object itself if the method is not found the engine then looks up the Prototype chain of the object utilizing the Prototype property each Constructor function in JavaScript has a prototype property which is shared by all instances of the Constructor this shared prototype is crucial for memory efficiency so Dem for example this we just create a Constructor function name programmer the two parameters being named and preferred language then we use the this keyword to assign it and the preferred language so now methods added to the Prototype are shared across all instances so I will expand this just so we can see it more easily we can do programmer so that Constructor function. prototype write code so we can assign this to an anonymous function and here we do log and back tick so we can use interpolation this. name writes code in this. preferred language end this with a semiconon we could also override the two string method for all instances so we can do programmer. prototype do two string assign this to an anonymous function say programmer this.name comma language this. preferred language and that with a sumon so now let’s create an instance of this programmer so I can say const JS programmer new PR programmer I’ll say Alice and the language is Javascript now let’s just call JS programmer. write code now we save it and here in the console we see the expected output so the advantages of using prototypes let me expand this again so we can see the code the First Advantage is memory efficiency since methods defined on the Prototype are shared there is only one copy of each method in memory memory regardless of the number of instances this is especially beneficial in applications where many instances of a class are created as it saves a significant amount of memory so for example if we were going to create many programmer objects they would all share these same methods so right code and this implementation of the two string method so the second Advantage is flexibility javascript’s Dynamic nature allows you to add or modify methods on the Prototype at any time modifications to the Prototype are reflected across all instances immediately which can be particularly useful for updating functionality at runtime and the third Advantage is overriding methods so you can easily override inherited methods by defining new implementations on the prototype for example the two string method for programmer has been overwritten to provide more specific information about each programmer instance managing instance and prototype members so first consider instance members these are defined within the Constructor function and these are unique to each instance such as the name and preferred language in the programmer Constructor these properties are set per individual object and manage data that varies from one instance to another now consider prototype members these are defined on the constructor’s Prototype and these members are shared across all instances like the right code and two string Methods this setup is optimal for methods that perform generic actions applicable to all instances by strategically using prototypes to share methods among instances you can enhance your job JavaScript applications both in terms of performance and maintainability this approach ensures efficient memory usage while maintaining the flexibility to adapt the shared behavior of objects how does using prototype based inheritance in JavaScript help in managing memory efficiently when dealing with numerous object instances using prototype-based inheritance in JavaScript helps manage memory efficiently because methods defined on the Prototype are shared among all instances of an object instead of each instance having its own copy of the method there’s only one copy stored in memory this significantly reduces memory usage especially when creating thousands of instances as all instances refer to the same method on the Prototype what are the advantages of defining a method on a constructor’s prototype as opposed to defining them within the Constructor function itself defining a method on a constructor’s prototype in JavaScript has several advantages one being memory efficiency methods on the Prototype are shared by all instances so only one copy of each method exists in memory saving space when creating many instances a second Advantage is consistency changes to a prototype method are immediately reflected in all instances making it easy to update functionality across multiple objects the third Advantage is performance shared methods reduce the memory overhead and can lead to better performance as there is no need to duplicate methods for each instance understanding prototype Dynamics in JavaScript so in JavaScript changes to a constructor’s prototype affect all instances regardless of whether they’re created before or after the changes this Behavior highlights javascript’s use of object references for prototypes consider the programmer Constructor function so just create this takes the name and preferred language as parameters we’ll set these properties so now let’s instantiate it I’ll set cons I’ll just call this programmer new programmer with the name of stepen in the language of JavaScript so now let’s add a new method to the programmer prototype so we do programmer prototype write code sending this to an anonymous function console.log say this.name writes code in this. preferred language end that with the semic and let me expand this so we can see the full method so even though programmer this instance was created before the right code method was added to the Prototype this instance can still access the right code method so let’s do that do programmer. write code we can save that and here in the console we see the console log statement Steven writes code in JavaScript so enumerating object properties so using a Forin Loop you can enumerate over all properties of an object including those on the Prototype so here we can do for let key in programmer we do log while the keys and let’s comment this out for now can save that now here we have enumerated over the properties so we have the name the preferred language and the method right code So based on the JavaScript documentation properties defined directly on the object are referred to as own properties while those inherited from the Prototype are called prototype properties so checking for own properties you can use the has owned property method me to determine if a property is an own method of the object so we’ll see an example of that do log programmer do has own property we’ll say the name output that and here we see the output of true let me comment this out we’ll clear it just so it’s easier to see so that the name property is an own method meaning that it was defined within the Constructor function so let’s see another example I’ll do shift option and down arrow to copy that and I’ll specify right code so this is the name of the method or the member that was defined on the Prototype here when we save this we get the value of false indicating that this is a prototype property so this method has own property helps distinguish between properties that are part of the object itself and those inherited from the Prototype understanding the distinction between own and prototype properties is crucial for working effectively with object or features in JavaScript this this lesson demonstrates the dynamic nature of prototypes and their practical implications providing a deeper understanding of how JavaScript handles object properties and inheritance how does adding a new method to a constructor’s prototype affect existing instances of that Constructor in JavaScript adding a new method to a constructor’s prototype in JavaScript makes that method available to all existing instances of that Constructor as well as any new instances created afterward this is because instances reference the prototype for methods so they automatically have access to any new methods added to the Prototype even if they were created before the method was added what is the difference between owned properties and prototype properties in JavaScript and how can you check if a property is an owned property of an object in JavaScript only properties are those defined directly on an object while prototype properties are inherited from the object’s prototype to check if a property is an own property of an object you can use the has owned property method if this returns true the property is an owned property if it returns false the property is inherited from the Prototype or from its parent while JavaScript allows you to extend the functionality built-in prototypes such as adding a shuffle method to array. prototype it is generally advisable to avoid doing so so here’s an example of what it might look like do array. prototype and we extend it by adding a shuffle method assigning this to Anonymous function and here I just add a comment this would be implementation of the shuffle so then when we create a new array assign this to an empty array then I’ll be able to call array. Shuffle so here let open up the tools let’s just log something out I’ll just do log and I’ll say Shuffle I save that it reach the output of Shuffle so this approach may seem convenient because we can add our own custom methods to builtin data types in JavaScript however it carries significant risk so there is a potential for Conflict for example Library conflicts if you modify a built-in prototype you risk conflicts with thirdparty libraries that might rely on the default behaviors of these objects different implementations of the same method can lead to inconsistent Behavior cross parts of your application as a best practice do not modify objects that you do not own this helps with maintainability and compatibility modifying objects that are globally accessible like built-in prototypes can make your code harder to manage and predict it may also break compatibility with future versions of Javas script or interfere with enhancements in third party libraries so for an alternative approach instead of modifying built-in prototypes consider a safer alternative you can use a utility function so rather than doing this if com that out can do function Shuffle array this takes in an array as parameter variable and here you have the shuffle logic here and then you return the array so then to utilize that can simply do cons shuffled array then you simply invoke that function and pass in the array now you can also extend the Prototype safely so if absolutely necessary you want to ensure your ification does not overwrite existing methods and check if the method isn’t already defined so for example you can do if type of array. prototype. Shuffle so if the type of is not a function meaning that’s not defined then if I just copy this and paste it here and uncommon that to tabs so this is an example of how you can extend the Prototype safely by adherance of these guidelines you to ensure that your jav code remains robust maintainable and compatible with other libraries in future updates why is it generally advisable to avoid modifying built-in prototypes in JavaScript it is generally advisable to avoid modifying built-in prototypes in JavaScript because doing so can cause conflicts with third party libraries that rely on the default behaviors of these objects modifying prototypes can also make your code harder to maintain and predict it might break compatibility with future versions of JavaScript or interfere with enhancements in other libraries what are some safer alternatives to modifying built-in prototypes in JavaScript and how can they help maintain code compatibility and predictability some safer alternatives to modifying built-in prototypes in JavaScript include using utility functions where you create Standalone functions to add new functionality without affecting built-in prototypes this avoids potential conflicts and keeps your code isolated and maintainable you can also extend prototypes safely so if you must extend a prototype first check if the method already exists to avoid overriding existing functionality these approaches help maintain co- compatibility and predictability by preventing conflicts with existing or future code and ensuring your additions do not interfere with standard JavaScript Behavior or thirdparty [Music] libraries so to summarize inheritance and prototypes in JavaScript this section has provided a thorough exploration of several key Concepts in JavaScript related to optic R programming we began by understanding inheritance including prototypes and prototypical inheritance which are fundamentals to how JavaScript handles objects and classes we discuss multi-level inheritance where objects inherit properties and methods across multiple levels allowing for a more structured and hierarchical object model the use of property descriptors was covered to control and manage our properties behave including their enumerability and figurability and writability further we examine the distinction between Constructor prototypes and instance members emphasizing the difference

and roles of each in JavaScript programming the process of iterating over both instance and prototype members was covered giving practical insight into how to access and manipulate object properties effectively lastly we address best practices regarding prototype manipulation specifically advising against extending built-in objects this practice while possible can lead to conflicts and compatibility issues especially when dealing with third party libraries overall this section aimed to equip you with a solid understanding of how inheritance and prot types contribute to efficient and effective JavaScript programming promoting better coding practices and a deeper understanding of the language’s [Music] capabilities what is the significance of prototypes and prototypical inheritance in javascripts handling of objects and classes prototypes and prototypical inheritance are crucial in JavaScript because they allow objects to inherit properties and methods from other objects this enables code reuse and efficient memory usage since methods can be shared across instances rather than duplicated prototypical inheritance also supports a flexible and dynamic object model allowing developers to extend and modify objects at runtime which is fundamental to javascript’s object orent programming capabilities how do property descriptors help manage the behavior of object properties in JavaScript and what attributes can they control property descriptors in JavaScript help manage the behavior object Properties by allowing you to control specific attributes of those properties the attributes they can control are innumerable this determines if the property shows up in the forn Loop and object. keys writable this determines if the property’s value can be changed and configurable this determines if the property descriptor can be changed and if the property can be deleted using property descriptors you can precisely Define how properties behave making your objects more secure and predictable why is it generally advised against extending built-in objects and JavaScript and what are the potential risk of doing so it is generally advised against extending built-in objects in JavaScript because it can cause conflicts with third party libraries that rely on the default behavior of these objects this can lead to inconsistent behavior and bugs additionally modifying built-in objects can make your code harder to maintain and predict and it may break compatibility with future versions of JavaScript or interfere with updates and other libraries a better practice is to use utility functions or safely extend prototypes by checking for existing [Music] methods when building software duplicating methods across different objects not only consumes more memory but also goes against the dry principle dry stands for don’t repeat yourself let’s consider how can use inheritance to share common functionality in a way that aligns with best practices imagine we have multiple types of programmer objects such as front-end programmer and backend programmer and they share some common behaviors instead of duplicating methods across both Constructors we can define a generic programmer object that contains shared methods so let’s define a base shape for our shared methods and we name it programmer now this will accept one parameter the should be name so we can set this property for the name and we can Define all of the shared methods that we want so we can do this. code assigning this to Anonymous function and here we log out this. name SCS coding then we can Define this. debug let’s extend this so we can see it more easily function and here we log out this. name is debugging and our last method this. meeting we log it out this. name is attending meetings so here let’s create two instances of this so we can say Alice we call a new programmer to call this Constructor function pass in the name and let’s duplicate so shift option and down arrow I’ll pass in Steven so now let’s do alice. code and steven. code here we save this and we see the expected console log statements so when you define methods directly within the programmer Constructor function each instance of programmer will have its own copy of these methods so here the instance of Alice will have its own methods for code debug and meeting as well as the instance for Steven this approach is less efficient in terms of memory usage because every instance has duplicate methods so remember functions are objects in JavaScript so let’s compare the code functions for these two programmer objects so here I comment this out and then I’ll log out alice. code so that reference and we’ll see if this is strictly equal to steven. code so we are comparing to see whether these functions reference the same object so we see the value of false so in this case Alice and Steven each have their own copies of the code debug and meetings method which is redundant and can consume more memory especially if you create many instances so here can clear this out and expand this so instead of defining these three methods in the Constructor function we can Define it in the Prototype so that these methods will be shared I can Define it here do programmer. prototype. code and then I can assign the function here and I’ll do the same with the other methods so programmer. prototype. debug we’ll copy this and paste it there now we have one more for the meetings programmer. prototype. meetings and then we will copy the implementation here now since we Define on the Prototype we can remove this so now when we compare these functions so alice. code and steven. code we saw the output of true because they are referencing the same function on the Prototype so these functions are shared amongst all instances so when you define methods on the programmer. Prototype all instances of programmer share the same method implementation so this is more memory efficient because the methods are not duplicated for each instance instead they are shared among all instances which is the essence of prototypical inheritance in JavaScript in this case Alice and Steven share the same code debug and meetings method which are defined on the Prototype this reduces memory usage and ensures that all instances benefit from many updates to these methods without needing to update each instance individually what are the benefits of defining methods on the prototype of a Constructor function in JavaScript and how does this approach align with the drive principle defining methods on the Prototype of a Constructor function in JavaScript provides two main benefits the first being memory efficiency methods defined on the Prototype are shared among all instances of the Constructor this reduces memory usage since each instance does not create its own copy of the method the second benefit is code reuse by using the Prototype you avoid duplicating code across multiple instances aligning with the drive principle this makes the code easier to maintain and update in summary prototypical inheritance allows for shared behavior and memory efficiency making your code more maintainable and performant so let’s summarize what we covered so far we implemented methods on the prototype for three reasons one is memory efficiency so defining methods on the Prototype ensures that all instances share the same method implementations reducing memory usage the second benefit is meth method sharing so prototype methods are shared among all instances making it easier to maintain and update the methods and the third is the benefit of inheritance prototypical inheritance leverages the shared Behavior allowing derived objects like front-end programmer and backend programmer to inherit and use these methods without duplication by defining methods on the Prototype you adhere to the principle of efficient memory usage in code reuse making your JavaScript code more maintainable and performant now let’s define more specific programmer roles you can expand this scrolling up we can create a front end programmer Constructor function so this also takes in a name and we’ll create our Constructor function for a backend programmer now we want to call the programmer Constructor function to initialize the name property so we want this version frontend programmer and back programmer to be derived objects that inherit from the programmer Constructor function so in order to call the programmer Constructor function we’ll do programmer. call now for the first argument we will pass the current context so we use the this keyword so this references this current object meaning the instance of the front-end programmer now for the second argument we will pass a name he because that is the expected parameter for the programmer Constructor function so here when we scroll up this Constructor function expects a name so we can also repeat this for the backend programmer so using programmer. call we are calling the programmer Constructor function and setting the context to the new instance of the front-end programmer or backend programmer this ensures that the name property is correctly initialized for each specific programmer type so for setting up the inheritance to enable the front-end programmer and backend programmer to inherit the methods from the programmer prototype we need to set the prototypes to be instances of the programmer Constructor function so to do that can do frontend programmer. prototype this is assigned to object.create programmer. prototype now we repeat this so shift option down arrow for the backend programmer I will also set the Constructor so frontend programmer. prototype. Constructor and set this to front end programmer and we’ll repeat that for the backend programmer so now front-end programmer and backend programmer instances can use the methods to find in program so was access to code debug and the meeting method so let’s actually see this here I will set this here we’ll clear it out let’s common out this console log statement and we’ll utilize these two instances we can do HST say Joe is new front end programmer the name of Joe so here we can say joe. code joe. debug and joe. meeting and we see the expected console log statements defined on the programmer prototype now let’s create an instance of the backend programmer so I can say const and I’ll say gen new backend programmer gen so we’ll call the same methods gen code move this up gen. debug and gen. meting and here we see the expected console log statements so this setup uses prototypical inheritance to share common methods among different types of programmers minimizing redundancy and enhancing maintainability by structuring objects in this way you effectively utilize javascript’s Dynamic nature and prototypical inheritance to create more efficient and organized code this approach ensures that all specific programmer types benefit from updates to the programmer prototype without needing to modify each Constructor separately adhering to efficient coding practices and the principles of object Orient [Music] design how does using programmer. call passing in for the first argument the this keyword and for the second argument passing in the name within the constructors of front-end programmer and backend programmer ensure proper initialization of the name property for these specific programmer types using programmer. call within the constructors of front-end programmer and backend programmer ensures proper initialization of the name property by calling the programmer Constructor with the current instance the this keyword so this way the name property is correctly set for each front-end programmer and backend programmer instance just like it would be for a programmer instance why do we use object . create and pass in for the argument programmer. prototype to set the prototypes of front-end programmer and backend programmer and what is the significance of resetting their Constructor properties we use object. create to set the prototypes of front-end programmer and backend programmer so they can inherit methods from programmer this allows instances of these objects to share the same methods making the code more efficient resetting their constructive properties ensuring the instances are correctly identified as front-end programmer or backend programmer maintaining proper type identification so recap and Core Concepts the term prototype in JavaScript essentially means the parent object in our Constructor functions we define properties and methods often we Define a general Constructor function like programmer which contains common properties and methods so in this case the name property and the code method however we may need to create more specialized objects such as frontend programmer which has specific capabilities instead of duplicating the properties and methods defin in programmer we use prototypical inheritance also called prototypal inheritance to reduce code duplication by doing this front end programmer so this will inherit the properties and methods from the programmer parent object when we call a method such as this code method JavaScript checks the front-end programmer object if it doesn’t find the method definition it looks up the inheritance chain to the programmer prototype and uses the method defined there this setup means we write less code which is easier to maintain and modify because the code is defined in one place and reuse as applications grow reducing code duplication through inheritance makes logical sense so addressing Constructor property issues in prototypical inheritance when implementing inheritance a common issue is the Constructor property this property is important for creating instances Dynam dynamically based on the Constructor function associated with the Prototype so let’s illustrate this with our programmer example here we have the parent object or the base object and we have the derived object the front-end programmer which is a more specialized version of the programmer Base by using programmer. call we inherit the name property but we also want to inherit its methods so to do this we would do frontend programmer. prototype assigned to object . create programmer. prototype right so add a commment here so this is setting up inheritance so we inherit methods so every object has a Constructor property which refers to the function called to initialize the object when we call new frontend programmer so here when we are creating instance a frontend programmer we wanted to call the front-end programmer Constructor this refers to this Constructor function however after setting the prototype to object.create and passing in programmer. Prototype as we did here to inherit the methods The Constructor property of frontend programmer. prototype points to the programmer Constructor function so it’s pointing to this Constructor function as opposed to this one so this can cause confusion so to demonstrate this can log it out say front end programmer. prototype Constructor and strictly equal to this Constructor function just to demonstrate that it is now referencing this Constructor function rather than the frontend programmer Constructor function that we wanted to so can resize this so we can see the output in our console and I’ll save it and here we see the value true so this shows that it’s referencing this Constructor function so to correct this we reset The Constructor property after changing the Prototype right so after we inherit the methods then we need to make sure that we’re referencing the correct Constructor function so to do this we would do front end programmer. prototype do Constructor and we assign this to the front-end programmer Constructor function so now here when we log this out if we save this again we see the value is false because the front-end programmer Constructor function is no longer referencing the programmer Constructor function so to recap whenever you change the Prototype of a function in JavaScript reset the Constructor property this ensures The Constructor property accurately reflects the actual Constructor function for instances preventing potential issues and object creation and inheritance this practice maintains consistency and predictability especially in complex inheritance hierarchies [Music] what is the primary benefit of using prototypical inheritance in JavaScript when creating specialized objects like front-end programmer from a general Constructor function like programmer the primary benefit of using prototypical inheritance in JavaScript is that it reduces code duplication by inheriting properties and methods from a general Constructor function like programmer specialized objects like front-end programmer can use those shared features without having to rewrite them this makes the code easier to maintain and update since the common code is defined in one place and reused across different objects why is it necessary to reset the Constructor property when setting up inheritance using object.create in JavaScript and what potential issues can arise if this step is omitted it is necessary to reset the Constructor property when setting up inheritance using object.create in JavaScript because object.create Chang es the Prototype which can mistakenly point to the wrong Constructor if you don’t reset it the Constructor property might refer to the parent object like programmer instead of the child object like front-end programmer this can cause confusion and bugs when creating new instances as JavaScript won’t know the correct function to use for initializing the objects how does JavaScript handle method lookups in the context of prototypical inheritance and what is the sequence of steps when a method like code is called on an instance of frontend programmer when a method like code is called on an instance of front-end programmer JavaScript follows these steps the first is checking the instance JavaScript first looks for the code method directly on the frontend programmer instance second check the Prototype if it doesn’t find the code method on the instance it looks up the Prototype chain to the frontend programmer. Prototype next it checks the parent prototype if the code method isn’t there it continues up the chain to programmer. prot type where it finds and uses the code method defined there this process ensures that the instance can use methods defined in its own class or any parent class following the inheritance chain so in objector programming in JavaScript Constructors play a crucial role in setting up new objects so Constructor functions essentially refer to the function that is called or invoked to instantiate an object with a given state so we will modify the programmer Constructor that we’ve been working on so we can do function we call it programmer and we’ll specify two parameters so the name and the specialization and we can set that here with the this keyword and this. specialization sign to specialization so now let’s create a derived Constructor function so this will be a more specific type of programmer which we will call a frontend programmer who will also have a preferred framework along with a name and specialization so we have function frontend programmer name specialization and preferred framework so to inherit the name and specialization properties from this parent object rather than having to duplicate that code we do programmer. call for the first argument we’ll pass in the this keyword so that refers to this current object and then we’ll pass in name and specialization because these are the two arguments needed because these are the two parameter variables defined in this programmer Constructor function so now that we’ve inherited those two properties we need to assign our preferred framework now that we implemented that let’s create an instance of front end programmer you can say cons say Steven new frontend programmer Steven for the name the specialization will be front end and the preferred framework speci for that to be react so react is actually a JavaScript library but in this context we will consider it a framework so let’s talk a bit about the new keyword when you use the new operator several things happen first is a new object creation so JavaScript creates a new object in memory second is setting the Prototype it sets the Prototype of this new object to the Prototype of the Constructor function from which it was called so it would be programmer. prototype if you were to do new programmer and it is frontend programmer. prototype for when you do new frontend programmer so third is executing the Constructor The Constructor function is called with the this keyword bound to the newly created object allowing properties and methods to be assigned to this and fourth is returning the object unless the Constructor explicitly returns a different object object the new object is returned by default so let’s discuss the this keyword so in the context of a Constructor function called with the new Operator by default the this keyword refers to the new object being created and second if the Constructor function is called without the new operator then it would refer to the global object so this would be the window object in browsers or the global object and no. JS which can lead to unexpected behaviors and errors Show an example of this here we log out the front end programmer name now do shift option down arrow to create those copies the specialization and the preferred framework let’s resize this so we can see our output in the console and clear this out and when we save it we get our expected output logging our properties so the key takeway using Constructor functions properly with the new operator ensures that the new objects are set up correctly with their intended prototypes and properties it is essential to use the new operator to avoid unintended side effects and ensure that the this keyword behaves as expected within the Constructor function this mechanism is fundamental for implementing inheritance and creating a hierarchy of objects in JavaScript explain the steps involve when the new operator is used with the Constructor function in JavaScript why is it important to use the new operator when calling a Constructor function when the new operator is used with a Constructor function in JavaScript the following steps occur first is a new object creation so a new JavaScript object is created in a memory second is set in the Prototype the new object’s prototype is such as the Constructor functions prototype third is executing the Constructor the Constructor function is called with the this keyword bound to the new object allowing properties methods to be assigned to it and the fourth step is R return the object the new object is returned automatically unless the Constructor explicitly returns a different object it’s important to use the new operator to ensure that the this keyword refers to the new object being created without the new operator then the this keyword will refer to the global object or be undefined if you were using strict mode leading to unexpected behaviors and errors so refactoring with the programmer function so suppose we have a base programmer class and specific subclasses like front-end programmer and backend programmer so here’s you can set up inheritance using a generalized extend function so we have our base programmer Constructor function and a method now let’s create our specific programmer types so that’s function frontend programmer with the name we call programmer. call This And name so let’s copy this and we’ll create our backend programmer so let’s define an extend function that automates the process of setting up prototypical inheritance between a parent and a child Constructor function so we can inherit the methods and properly assign The Constructor function so you can do function extend so for the first parameter variable I’ll specify that to be the child object or child class the second will be the parent so we want to inherit the methods of the parent so we do child. prototype is assigned to object.create parent. prototype so then we will assign The Constructor prototype. Constructor to the child so now using the extend function so with this extend function implemented you can easily set up inheritance for any any number of specific programmer types by simply calling it so we’ll just do extend front end programmer and programmer so I’ll do shift option and down arrow and I’ll pass in backend program so now let’s test the implementation I’ll resize this so we can see in our console so we’ll create instances of the frontend programmer so I say cons Steven sign to new front-end programmer and I’ll do shift option and down arrow and I’ll just change this to be backand programmer with the name of Alice so now we can call and invoke the method that we inherited which is the code method here so it is defined on the parent object which is programmer so we can do steven. code and we could do alice. code and here save it we get the expected output so the benefits of using the extend function the first is encapsulation so by encapsulating The Inheritance logic in the extend function we avoid redundancy and make the code more maintainable and second is reusability the extend function can be reused across the project wherever inheritance is needed promoting consistency and reducing the chance of errors this approach not only streamlines The Inheritance process but also makes the code base more organized and easier to manage by using a generalized method for extending prototypes you ensure the old derived classes correctly inherit from their parent class without manually setting the Prototype and Constructor each [Music] tire what are the benefits of using a generalized extend function to set a prototypical inheritance in JavaScript explain how it improves encapsulation and reusability in your code using a generalized extend function to set a prototypal inheritance in JavaScript has several benefits one being encapsulation the extend function wraps The Inheritance logic in one place so you don’t have to repeat the same code for every new child Constructor this makes your code cleaner and easier to maintain and the second benefit is reusability once you have the extend function you can use it whenever you need to set up inheritance saving time and reducing the chances of mistakes this ensures consistency across your code base overall it makes your code more organized and easier to manage to demonstrate method overwriting we’ll redefine the code method in front-end programmer to include additional Behavior specific to front-end programming So currently we have this derived object the frontend programmer which inherits the properties and methods from the base programmer object so when we call or invoke the code method it simply calls the function derived in its parent but we can override this function it so here before I instantiate it I will scroll up so I’ll resize this then before instantiating it so I can say frontend programmer. prototype. code and assign this to an anonymous function so I’ll say programmer so that Constructor function for the parent. prototype. code. call and then I’ll pass the this keyword so this calls the base implementation defined up here now I can say log and I’ll do back ticks this.name is coding in HTML CSS and Java script so now I will save this and we’re invoking the code method on a frontend programmer we can save it let’s restart the live server so command shift and P live server open let’s resize this right I’ll close this one out open up the developer tools so command shift and J so now I close the sidebar with command b or controlb and I get the expected output I get Steven starts coding which is the output defined in the programmer implementation of the code method and in this derived object where we did method overwriting I also log out Steven is coding in HTML CSS and JavaScript so an explanation of method overwriting this setup showcases how a prototypical inheritance Works in JavaScript when you call the code method on an instance of frontend programmer JavaScript first checks the frontend programmer prototype for this method since we’ve overwritten code in front-end programmer this version is executed which also calls the Base Class method to maintain the general programming Behavior then add specific Behavior so if I were to comment this out it would simply overwrite it and simply log out what we Define here right so just this expected output so some key points the first is Method lookup javascript’s prototype chain means that method lookup starts with the object itself and moves up the chain until it finds the method or reaches the top of the chain and second using the call method for base methods to include the Base Class methods functionality when overriding methods use call to specify the context passing in the this keyword and ensure the base method executes correctly for the deriv class instance by following these principles you can effectively manage and extend behaviors in JavaScript allowing for more flexible and reusable code [Music] structures how do you override the code method in frontend programmer to include additional Behavior while still calling the Base Class method to override the code method in frontend programmer and include additional Behavior while still calling the Base Class method you could do the following first you would Define the new code method on frontend programmer. Prototype inside this method you call the base code method using programmer. prototype. code. call and passing in the this keyword and this will keep the original behavior and then you would add the new Behavior specific to front programmer this way when code is called on a front-end programmer instance it will first run the base code method and then add the new Behavior what is the significance of using call when invoking the Base Class method in an overb method in JavaScript using call when invoking the Base Class method in an overwritten method is important because it ensures the base method runs in the correct context by using call you pass the current object which would be the this keyword to the Basse method so it behaves as if it was called directly on that object this allows the base method to properly access and modify the object’s [Music] properties polymorphism is a key Concept in objectoriented programming so polymorphism stands for many forms and it is what allows objects of different classes to be treated as objects of a common super class through inheritor it’s essentially the ability for different objects to respond to the same method call in different ways first let’s look over this starting code that we’re using we have the extend method which is a utility function that we’re using so that a child object can inherit methods from parent object and make sure that we are resetting the Constructor we have a base object for our programmer which just sets a name property and we Define a method named work who simply logs out a string then we have two derived objects front-end programmer and backend programmer so both of them inherit the name property from this Bas programmer object and we are calling the extend method so we’re inheriting the work method so now we have this spoiler play code let me resize here so implementing polymorphism we have our specialized programmer types which is front-end programmer and backend programmer when want each of them to have a unique implementation of the work method before instantiating an instance of front-end programmer we can do frontend programmer. prototype. workor and assign this to an anonymous function so we are overwriting this method we can do log and we’ll do back tick is designing and coding the front end we have implemented that method overwriting implementation now we can do backend programmer. prototype. workor sign this to Anonymous function and we will log it out back ticks we can say this. name is developing server side logic right let’s create a backend programmer so I’ll scroll up and I’ll do shift option and down arrow and I’ll just name this to be Alice Alice and backend programmer so we’ve instantiated two instances so one for the frontend programmer and one for the backend programmer so using polymorphism so let’s create an array of programmer objects which can be either a front-end programmer or backend programmer so since we are utilizing inheritance we know that a frontend programmer is a programmer and backend programmer is a programmer right so the concept of is a is very important such that our in makes logical sense so by creating this array we’ll say programmers this will demonstrate how each object can use the work method differently according to their specialized class definition so create an array and first I’ll pass in Steven so that front- end programmer and Alice the backend programmer so now let’s iterate through this programmer’s array I can do that with a for of loop so I’ll say for for let programmer of programmers and it will call programmer. workor and so now it will call its unique implementation of the work method so the frontend programmer will call this method and the backend programmer will call its own implementation of the work method so now let’s save this and we’ll see the output in the console so now on the right we see Steven is designing en coding the front end and for the backend programmer Alice is developing server side logic so some key points the first is no type checking is needed so with polymorphism you don’t need to check the type of each object before calling the work method each object knows its own implementation of the work method allowing them to behave correctly according to their specific type and the second is code flexibility and reusability polymorphism simplifies code management and enhances its reusability by allowing you to use a general interface for a range of different objects this example demonstrates how polymorphism can be leveraged in JavaScript to interact with objects from different classes through a common interface enabling flexible and easily manageable code this approach is particularly useful in systems where new types might be added but existing code shouldn’t need extensive changes to accommodate them how does polymorphism allow different objects to respond to the same meth method call in different ways polymorphism allows different objects to respond to the same method call in different ways by using method overloading each object even if they are of different classes can have its own version of a method so when a method is called the correct version for that specific object is executed what are the benefits of using polymorphism in terms of code flexibility and reusability as demonstrated by the programmer example polymorphism increases code flexibility and reusability by allowing objects of different types to be treated through a common interface in the programmer example it means that you can call the same method in this case it is the work method on any programmer object without worrying about a specific type making the code simpler and easier to extend with new types of programmers [Music] understanding inheritance in composition with the programmer function while inheritance is a powerful feature in object Orient programming it’s important to use it carefully to avoid creating overly complex and fragile systems so potential issues with inheritance inheritance should always satisfy the is a relationship meaning that a subass should represent a more specific version of the super class for instance a front-end programmer which is the subass or drive class is a specific type of programmer with programmer being the super class or Base Class however problems can arise if the subass inherits methods that do not logically apply to it leading to an inappropriate relationship example of inheritance complexity so consider a scenario where you are expanding the programmer function to include different types of technical staff in a company so I can resize this Implement a base object so this will be an employee object which has a name parameter this. name and we’ll set the name value now we can create a more specific version of an employee so this subass would be programmer so it takes in a name and we call employee. call then the this context for the first argument referring to this programmer object and and the name so this now inherits the name property if we can create another subass or derived object and this would be a manager so this will also inherit from the employee based object so a programmer is an employee and a manager is an employee so it satisfies the is a relationship so I can call employee. call this and the name so manager inherits from employee now if the employee had programming methods those methods would not logically apply to a manager object so this example shows that the inheritance hierarchy can become inappropriate and bothersome as you don’t want to inherent methods that don’t make logical sense so this would happen in the case if this. employee had a method like code and then we’ll log out right code so it would make logical sense for a manager to have that functionality clear that so as a best practice you want to limit The Inheritance depth in general it’s best to keep inheritance hierarchies shallow ideally not going Beyond one level deep inheritance trees can become difficult to manage and understand favoring composition over inheritance an alternative to inheritance is composition where you build classes out of components rather than using a strict parent child relationship this approach often provides greater flexibility and reduces dependencies between classes when you think of the term composition imagine it as a has a relationship whereas inheritance represents and is a relationship with composition an object includes instances of other objects and their functionality allowing it to have the behavior it needs without relying on hierarchical structure implementing composition with mixins in JavaScript composition can be achieved using mixins where functionality can be mixed into a class for example instead of having a programmer inherit all behaviors specific functionalities like can code can review can design might be mixed in as needed so const can code which would be a JavaScript object literal and within it we can have a method for coding so I’ll say log and I’ll say this.name is coding I can Define another object say can review and I will Define a review method the log and I can say this.name is reviewing code so now let’s actually move this up so I move it up with shift and the up Arrow so I’ll just reorder that so we have these objects defined before the implementation of our programmer Constructor function so let’s create an instance of a programmer so I’ll say cons Steven equals new programmer just pass in my name so now for this programmer Constructor function to utilize the code method and review method we can do object. assign this as the first argument and we’ll pass in can code and can review so I can add a comment here scroll up and I’ll say composing the object with necessary functionalities so now let’s create an instance of programmer so I can say con Steven equals new programmer I’ll pass in my name so then I can do steven. code and steven. review I and save that and I get the expected output so in summary in software design while inheritance might seem like a straightforward way to reuse code it’s essential to evaluate whether it introduces unnecessary complexity often composition provides a more flexible and robust alternative allowing objects to be constructed from discreet reusable behaviors this approach aligns with the principle of favoring composition over inheritance help me to maintain clean and manageable code [Music] bases what is composition composition is a design principle where an object is made up of one or more other objects allowing it to use their functionality it represents a has a relationship meaning that an object contains and uses other objects rather than inheriting from a parent class what are potential issues with inheritance and why is it important to ensure that a subclass satisfies the is a relationship with its super class potential issues with inheritance include creating complex and fragile systems if subclasses inherit methods that don’t logically apply to them it’s important to ensure that a subass satisfies the is a relationship with its super class to maintain logical consistency for example a front programmer should be a specific typee of programmer how does composition offer a more flexible alternative to inheritance in software design and how could it be implemented in JavaScript using mixins composition offers more flexibility than inheritance by allowing objects to include and use functionality from other objects avoiding complex hierarchies in JavaScript it could be implemented using mixins where specific functionalities are added to an object as needed this way you can add functionality without relying on inheritance what is a mix in a Mixon is a reusable piece of code that adds specific functionality to objects or classes in JavaScript mixin are used to share Behavior across multiple objects by copying properties and methods into [Music] them in JavaScript object. assign is a powerful method used used to copy properties from Source objects to a Target object this capability is particularly useful for implementing mixins where common functionalities can be shared across different objects without forming a rigid inheritance structure here’s how you can apply this to a programmer function allowing programmers to have modular capabilities like eating walking and coding so defining mix and objects first let’s define simple objects that contain methods which can be mixed into any Target object so we can Implement a can e method and within it has an e method set this to an anonymous function so I can say this. hunger is decreased and I can log use back ticks this do name is eating so end that with the semicolon now Implement two other objects so the next will be can walk it will’ll have a walk method so I’ll say a function and we will log it out I’ll say this. name is walking we end that with a semicolon and then we have can code so can have a method coding and we will log out this. name is coding end that with a semicolon I’ll just add a period here just to be consistent with the other strings that we’re outputting so using object. assign to mix capabilities you can use object. assign to add these capabilities to a programmer so I scroll up I’ll Define a Constructor function for a programmer this takes in a name parameter variable so we set the name and we’ll set a property for the Hunger so this will be the default hunger level so now we have the mixin functionalities into the programmer’s Prototype so you can do object. assign programmer. prototype so this would be the Target and the source objects that we want to copy will be can eat can walk and can code so now we can instantiate a programmer so I’ll say cons programmer and then new programmer passing in my name and I call each of these methods so first let’s just log this out I can log programmer let’s resize this so we can see it in the console and I’ll save it so here when we expand we see the property for hunger and the name right so our expected properties so now let’s call programmer. Cam see programmer. e and then I’ll do shift option down arrow just to make copies of this and then I’ll say walk and then I’ll say code save that and here I get the expected output so Steven is eating Steven is walking and Steven is coding so to create a reusable mix and function to stream the process of mixing capabilities into different objects you can create a reusable mixin function so let’s define that just at the top so I can say function and I’ll name it mix in now for the parameters we’ll specify a Target object and we will use the rest operator with three dots sources so we can pass in one or more values as an argument so we’ll utilize object. assign the Target and then we will spread the sources right so now when we use this rather than doing object. assign let’s expand this so we can see it better so now I can comment this out and we utilize our Mix end function so here I can say mix in so the target is programmer and we can pass in a variable number of arguments ments so I’ll say can eat can walk and can code so let’s resize this and when I save it I get the same expected output so this approach demonstrates the flexibility of composition over inheritance by composing objects from smaller function Focus objects you can easily extend functionality without the constraints of strict class hierarchy this method not only makes your code more reusable but also makes it modular and easier to understand using Mixon with object. assign allows for dynamic capabilities to be added to objects promoting code reuse and reducing the complexity typically associated with deep inheritance hierarchies this method aligns well with the modern JavaScript best practice of favoring composition over inheritance providing greater flexibility and easier maintenance [Music] how does using object. assign facilitate the implementation of mixins in JavaScript and what are the benefits of this approach compared to traditional inheritance using object. assigned in JavaScript makes it easy to implement mixin by copying properties from multiple Source objects to a Target object adding new capabilities without using inheritance this approach offers greater flexibility avoids complex inheritance hierarchies and promotes code reuse by allowing you to combine only the needed functionalities this section delved into several Advanced topics essential for mastering object or programming in JavaScript we covered creating her own prototypical inheritance so we explored how to establish custom inheritance chains using javascript’s prototype base inheritance system we covered resetting the Constructor the importance of properly resetting the Constructor property when modifying object’s prototype was emphasized to maintain proper linkages we covered calling the super Constructor so techniques for invoking a superclass Constructor within a subass were discussed to ensure that inherited properties were correctly initialized we covered intermediate function inheritance We examined how to implement inheritance through intermediary functions enhancing flexibility and how inheritance is applied we covered method overwriting the course covered strategies for overwriting methods in sub classes to tailor or enhance functionality derived from a super class we covered polymorphism we discussed how polymorphism allows objects of different classes to be treated as objects of a common super class facilitating flexible and dynamic code we covered when to use inheritance guidelines are provided on appropriate scenarios for using inheritance focusing on maintaining a clear is a relationship and we cover mixin the use of mixin was introduced as a flexible alternative to inheritance for composing objects with multiple behaviors or capabilities without forming rigid hierarchical structures by understanding and applying these advanced concepts you can write more robust maintainable and scalable JavaScript applications this knowledge will enable you to leverage the full power of object R programming in JavaScript adapting to various programming challenges with effective Solutions so let’s go over modern JavaScript classes which is syntactic sugar over prototypical inheritance in modern JavaScript the class syntax provides a cleaner and more intuitive way to define Constructor functions and manage prototypical inheritance this new syntax simplifies the creation of objects and their prototypes even though it is essentially syntactic sugar over the existing prototypical inheritance model this syntax introduced in es6 which stands for ecmascript 2015 is part of a specification that enhances JavaScript by adding new language features to modernize it so consider the traditional Constructor function for a programmer that we’ve been working with so if I use the function keyword and I name it programmer I specify two parameters name and prefer language then I set the properties with the this keyword so this.name is assigned to name and this. prefer language is assigned to Preferred language Now to create a method I’ll use the this keyword and I’ll name My Method code signning this to an anonymous function so let’s log to the console back tick this. name is coding in this do preferred language so now I can create an instance of this with the new keyword to create a new object in memory so I’ll say cons programmer is assigned to new programmer I’ll pass in my name Steven and the preferred language is Javascript so now I can call programmer. code and we can output that to the console and here we see our expected console log statement so let’s rewrite this Constructor function using modern class syntax which makes it clearer and more structured so we can comment this out so this is the syntax that you would use in modern JavaScript applications you would use the keyword class and then you name that class so in this case it’s programmer and now you would Define a Constructor function so classes in JavaScript have one Constructor function and this is the function that has called when you use the new keyword so it is named Constructor right so that’s the keyword and in this case the parameters our name and preferred language and within it we set our properties so this not name set a name in this preferred language is set to Preferred language so now to Define our method we’ll name it code and we will log the same output statement so let me just copy it here just to save us some time so this is the modern way to define our classes in JavaScript rather than using Constructor functions so and when we save it we will get the same output right so once again we get step’s coding in JavaScript so understanding the underlying functionality despite the use of the class keyword the underlying me mechm Remains the Same so consider the type of operator even with the class syntax programmer is still a function in terms of javascripts type system it’s specifically a Constructor function so let’s log that out so I can demonstrate that and then I do log and then tab if I do type of and then programmer we will see that the type is a function so when we save this we see that it is a function es5 compatibility for environments that do not Support es6 classes tool like Babel available at babeljs doio can trans file this modern JavaScript back to es5 compatible code ensuring that the classes work across all browsers so consider the benefits of using class syntax the first benefit is Clarity and simplicity the class syntax is easier to read and understand especially for developers coming from other object oriented languages like Java or CP the second benefit is encapsulation using class syntax encourages better encapsulation and a more declarative structure for defining object Constructors and methods and the third benefit is standardization it offers a standardized way of object creation and inheritance that aligns with other program languages using the learning curve so in summary by utilizing modern JavaScript class syntax you could write cleaner more maintainable code while still leveraging the powerful prototypical inheritance model that JavaScript offers this approach not only enhances readability but also simplifies complex coding structures making it an essential skill for developers working in modern JavaScript environments how does the class syntax and modern JavaScript improve the process of defining Constructor functions and managing prototypical inheritance the class syntax in modern JavaScript makes it easier and clearer to create objects and their prototypes it provides a straightforward way to Define Constructor functions and methods making the code more readable and organized compared to the older method even though it looks different it still works the same under the hood what are the benefits of using class syntax over traditional Constructor functions in JavaScript there are three main benefits of using class syntax over traditional Constructor functions in JavaScript the first being Clarity the class syntax is easier to read and understand the second benefit is encapsulation it helps organize code better by keeping related methods together and the third benefit is standardization it aligns with how other program languages handle classes making it easier to learn and use so for your exercise update this function Constructor to use the es6 class syntax so here I’ll call item. display and I get the output of the name of the item and the quantity so to implement this I’ll comment this out so now I’ll do class and name the class grocery item then curly braces and then I’ll Define The Constructor function which will be executed when I use the new keyword so the parameter is the name and the quantity I just assign this with the this keyword to set the properties and for the quantity Now define a method so I’ll say display and I’ll just copy this console loog statement and face it here so let’s clear our console and I’ll save it and we get our expected [Music] output in JavaScript functions can be defined using either function declarations or function Expressions both methods serve similar purposes but have key differences in Behavior particularly regarding how they are hoisted so let’s consider function declarations function declarations are hoisted to the top of their containing scope this means that they are moved to the top during the compile phase allowing you to call them before they are physically defined in the code so to demonstrate this I’ll Implement a function I’ll name it GRE and then I’ll log out hello world now to demonstrate function hoisting I can call or invoke the Greet method before it is defined so if I save this I get the expected output so because of hoisting JavaScript will move this function to the top of the file during the compile phase so now considering function expressions in contrast function expressions are not hoisted which means you cannot call them before they are defined in the code trying to do so will result in a reference error so to demonstrate this I’ll just comment this out we don’t need it I can say cons say goodbye set this to an anonymous function and then we will log out goodbye so now if I try to invoke it for it is defined let’s clear this out and I save it here we see we get a reference error so you can comment this out so now let’s apply this concept to the programmer class context so we scroll up now let’s consider this class that we defined in our previous lesson when working with classes it’s crucial to understand that like function Expressions class declarations are not hoisted this means you must declare a class before you can instantiate it so let me move above it just to demonstrate that we cannot instantiate it before it’s being defined I can say conev is assigned to a new programmer I’ll say my name and the preferred language of JavaScript and I’ll just save that and here we see we get a reference error we cannot access programmer before it’s initialized so using class Expressions just as with function Expressions classes can also be defined using a class expression syntax which is not hoisted and allows for more Dynamic declarations so to demonstrate that I’ll just to find this here I can say cons my programmer class set this to the keyword of class and then curly braces and then I want it to have the same functionality as this programmer so I’ll just copy this over let’s clear let’s common out this line so we don’t need that so we’ve created this class expression and let’s create an instance of it below its declaration so I can say con programmer and new my programmer class pass in Steven and in this case I’ll say JavaScript and then we can call the method programmer. code let’s clear this out and we’ll save it and we get our expected output so here we are creating instance of it after its declaration now if I were to move it up so I’m moving it up with option up Arrow end up here so now that I try to instantiate instance of this before its declaration if I save it now then I get a reference error note that you wouldn’t actually use this class expression syntax very often but I wanted to demonstrate it just show that it is possible in conclusion choosing between function declarations and expressions or class declarations and expressions can impact how you structure your JavaScript code for Simplicity and Clarity especially when defining Constructors and methods within a class using class declaration syntax is often preferred however being aware of hoisting rules is crucial for avoiding runtime errors and ensuring that your JavaScript code executes AS intended [Music] what is the main difference in Behavior between function declarations and function Expressions regarding hoisting in JavaScript the main difference is that function declarations are hoisted to the top of their scope so you can call them before they are defined in the code function expressions are not hoisted so you must Define them before calling them otherwise you’ll get a reference error why is it important to understand hoisting rules when working with class declarations in JavaScript it’s important to understand hoisting rules because class declarations are not hoisted this means you must define a class before you use it or you’ll get an error knowing this helps you avoid mistakes and ensures your code runs [Music] correctly an object going in programming especially within JavaScript classes we distinguish between instance methods which act on instances of the class and static methods which are called on the class itself and are often used as utility functions so let’s consider the programmer class that we have defined so whenever we create an instance of a programmer it has access to the code method to demonstrate that we have dev. code when we save that we get the expected output which is this console log statement so now let’s define a static method which should be accessible through the programmer class so I’ll use the static keyword and then I’ll name this method compare skill and this will accept two parameters so I’ll say programmer one and programmer 2 and this will return a Boolean value comparing programmer one and their preferred language and strictly equal to programmer 2. preferred language so let’s create another instance of this programmer so I’ll do shift option and down arrow to create a copy and I’ll name this Dev to I’ll change the name to be Alice now to compare it I will log the result of that pan value so I’ll use let me scroll up and see better and I’ll say log I’ll do programmer and then the static method so I do dot compare skill now I’ll pass in Dev and Dev 2 and we’ll expect this to be true because they’re using the same programming language so when I clear this first and then save it so we get the output of true because they both have JavaScript as their preferred language so let’s scroll back up so we can review our class so instance methods like code are used to perform actions that are relevant to the individual objects created from the class and static methods such as compare skill are used for operations that are relevant to the class as a whole or involve multiple instances of the class but don’t depend on any single object state so understanding the utility of static methods static methods are particularly useful for utility functions where the operation does not depend on the state of a particular instance but rather on the parameters provided to the function this makes them similar to functions provided by the math object in JavaScript such as math. round or math.max which perform General utility operations and are not tied to a specific object in conclusion understanding when to use instance methods versus static methods in your javascrip classes can significantly impact the design and functionality of your applications instance methods are best for manipulating or utilizing the state of individual objects while static methods are ideal for tasks that require a broader scope ones that involve the class itself or interactions between multiple instances this distinction helps in organizing code logically and maximizing the efficiency and readability of your JavaScript applications what is the difference between instance methods and static methods and JavaScript classes instance methods are used on individual objects created from a class and act on the data within those objects static methods are used on the class itself and are typically utility functions that don’t rely on the data of any single object why are static methods useful in JavaScript and when should they be used instead of instance methods static methods are useful for tasks that don’t depend on the data of a specific object but rather on parameters provided to the method they should be used for General utility functions or operations involving multiple instances of the [Music] class so for your exercise to add a static method to the grocery item class you can Define the method with the static keyword so static methods are called on the class itself rather than on instances of the class so for your exercise create two instances of the grer item class and have each of these objects have different names and quantities then Implement a static method named compare quantities to compare the quantities of the two items and print out the result so if the quantity of item number one is greater than item number two then log that the name of the first item has more quantity than the name of the second item if the quantity of item one is less than item two then log that the name of item two has more quantity than the name of item one otherwise output that both of them have the same quantity so to implement the compare quantities static method I’ll use the static keyword and we name it compare quantities then it takes in item one and item two then I’ll use an if statement so if item 1. quantity is greater than the quantity of item two qu then I will log use back tick so I can use interpolation item one. name has more quantity than item 2. name else if item 1. quantity is less than item 2. quantity then I will log out item 2. name has more quantity than let’s fix this move that y then item one. name else will be the case when they’re equal and log out item one. name and item 2.n name have the same quantity so let’s create two instances of the grocery item class so I’ll say cons I’ll call this apple equals new grocery item and then the name is Apple and the quantity is four so I’ll just copy this line with shift option and down arrow and I’ll rename this to be banana let’s just copy this over and I’ll update this value to be seven so now I can call this static method with grocery item do compare quantities of apple and banana so let’s save that and here we get the expected output that banana has more quantity than Apple let’s switch these values around just so we get the expected result we’ll clear it out and then we say it you get apple has more quantity than banana and in the case when they’re equal we get the apple banana have the same quantity let’s go over understanding the this keyword in different contexts with the programmer class the this keyword in JavaScript behaves differently based on how a function is called this Behavior can lead to unexpected results especially when functions are detached from the object context so let’s first illustrate this with a programmer Constructor function so we’ll use the function keyword we’ll name it programmer this accepts a parameter of name so we’ll set the name property then we’ll Implement a method named code so we assign this to an anonymous function then log and then tab and we will log out the this keyword so let’s create an instance of the programmer object so we’ll name it programmer assign to a new programmer and I’ll specify my name so Steven and then I will call the code method so now want to Output this and save it here I see outputs this instance of the programmer so that object and memory so here we see the property of the name and the code method so now let’s consider detaching a method when you detach a method from its object and call it independently the this keyword loses its original context in JavaScript functions are objects so we know that this method or in other words this function is just an object in memory so to get access to it I can call it detach code methods and I set this to a reference to that object right so functions are objects and so now this identifier detach code will reference this function however because it’s detach it has lost context of its this keyword so now let’s invoke this so I can say detach code and then let me clear this out so we can see it and so when I save it here I see in the original instance when I call code it logs out the programmer object however when I call detached code it logs out the window object so in web browsers the this keyword will reference the window object and in nodejs it will reference the global object so how can we fix this we can utilize strict mode so we go up here in JavaScript strict mode changes the behavior of the this keyword in function calls not associated with an object so in strict mode the this keyword becomes undefined instead of defaulting to the global object so if I were to use use strict a string end it with a semicolon and I would specify this to be the first line in the program so now let’s clear this out and when I save it the first time when I call the code method and it console logs the this keyword it references the current object that it’s referring to however in the case when we call a detach method previously it was referencing the window object but now since we’re in strict mode it outputs undefined so here we’re using a Constructor function now if we were to to use classes they implicitly use strict mode to avoid these issues instead of using a Constructor function I’ll specify it to be a class so I Define The Constructor method this sets the name property and I’ll Define a method for code and it outputs to this keyword so let’s comment this out so we don’t need to explicitly specify use stript let’s clear this out and when we save it so because we’re using the class syntax it is implicitly using strict mode so let’s cover the benefits of strict mode in class bodies the first benefit is safety it prevents functions from unintentionally modifying Global variables which can lead to difficult to track bugs and the second benefit is consistency it ensures that the this keyword behaves consistently making the code more predictable and less prone to errors in conclusion understanding how this keyword behaves in different context is crucial for JavaScript development ERS by using strick mode and being cautious of how methods are called developers can write more robust and secure code the implicit use of strick mode within class bodies in modern JavaScript helps enforce these best practices preventing common mistakes associated with the this keyword in global [Music] context what are the potential consequences of detaching a method from its object context in JavaScript detaching a method from its object context in JavaScript can cause the this keyword to lose its original reference instead of pointing to the object it belongs to that this keyword May point to the global object like window in browsers or be undefined in strict mode this can lead to unexpected behavior and bugs because the method no longer has access to the object’s Properties or methods how does strict mode in JavaScript enhance code safety and consistency particularly in the context of class body strict mode in JavaScript makes code safer and more consistent by changing how certain things work in class bodies it ensures that

the this keyword is not accidentally pointing to the global object instead if the this keyword is not set it will be undefined which helps prevent bugs strict mode also stops you from making some common mistakes like creating Global variables by accident making the code easier to understand and less prone to errors so understanding abstraction with the programmer class abstraction and programming involves hiding complex implementation details and exposing only the necessary parts of an object this is commonly achieved through private properties and methods let’s apply the concept of abstraction to a programmer class where certain details like the programming language proficiency level might be internal to the programmer’s operations let’s consider the first approach where we achieve PR private properties through the naming convention so one approach is to use an underscore prefix to indicate a private property so if we create a programmer class and we have the Constructor picking a name in language then we can do this doore language language assign to language I’ll just add a comment here it’s not truly private just a naming convention so now if we were to instantiate it cons programmer new programmer passing in Steven and the language of JavaScript here I log out it do programmer doore language so here it outputs JavaScript so we still have Public Access but the use of the underscore indicates to the programmer that this is supposed to be a private property now there are issues with this and the issue is that this method relies on the naming convention and does not provide true privacy properties are still accessible from outside the class so let’s consider a second approach which uses es6 symbols a more secure way to implement private properties is using es6 symbols which provides a way to create unique identifiers so before I create my class I will saycore language instead it to a symbol value which is a unique identifier unique value so rather than setting it through notation underscore language I’ll use the square bracket notation and I’ll pass in the symbol as a key just to demonstrate this this is more private but still accessible through reflection so here if we try to access underscore language that’s not a property defined in it so we can actually access this but it is not straightforward but the demonstrate you could I will log out object. getet own property symbols it’ll pass in the identifier for our object let’s save that so here we see an array of symbols so using this if I want to get the value at the zeroth index I could do so so if I want to access that value at the zeroth index I can say cons language symbol it’s assigned to and not just cop this value over and the zeroth index so I can use this as the key in order to get the language do log programmer and then square bracket notation the language symbol and it outputs the value of JavaScript so here we see that this property is still accessible through the outside although it is not intuitive so some observations symbols provide a pseudo private mechanism as they are not accessible through normal property access methods however symbols can still be accessed through object. getet own property symbols so it’s not completely private so let’s consider private methods using symbols similarly you can use symbols to create methods that are not accessible directly via the class instance so let’s say if I were to define a symbol I’ll say underscore code and set that to a new symbol so unique value now I can create a private method so use square bracket notation then the symbol as the name of that method and then let’s log and I’ll say this.name is coding in and I’ll say thisor language and that with a period and a semic so in conclusion while symbols enhance privacy they do not provide a foolproof solution for private properties or methods for truly private class Fields es 2022 introduces private class fields and methods using the hash symbol or the hash prefix so this also called the pound symbol or Octor symbol but I’ll refer to it as the hash symbol and this is the best approach going forward for ensuring data encapsulation and adhering to the principles of abstraction and object orent programming so let me clear all this so we can start from scratch I’ll clear this out now we can say class programmer now I’ll create a private property name it language and here we see it as prefix with the hash symbol now let’s define our Constructor which takes in a name in a language and we do this dot language is assigned to the language and let’s set the name to this. name the name now we can define a truly private method we can do so with hash and then code so we can say log coding in thish language now let’s create an instance of this class so we’re creating a new object and memory programmer passing in my name and the language let’s log this programmer object and when we output it we can expand it and we see the name and the language now if we try to access the property of language let’s try doing that here programmer dot if I do hash and then language here we see the private fi hash language must be declared in enclosing class so in other words it is not accessible if wey to access it by language we get the value of undefined so this method ensures that the language property and code method are completely private it encapsulated within the programmer class and not accessible from outside this approach align closely with the principle of abstraction keeping implementation details hidden and interfaces clean and [Music] straightforward what are the benefits and limitations of using symbols for creating private properties in JavaScript classes you using symbols for private properties in JavaScript classes has benefits and limitations now the benefits are improve privacy symbols make properties less accessible through normal methods adding a layer of privacy another benefit is unique identifiers symbols create unique property Keys reducing the risk of naming collisions now the limitations the first limitation is that it is not fully private properties created with symbols can still be accessed using methods like object. get own property symbols another limitation is complexity using symbols can make the code harder to read and understand as accessing these properties isn’t straightforward how do private class Fields introduced in es 2022 improve data encapsulation compared to previous approaches private class Fields introduced in es 2022 improve data encapsulation by providing true privacy for properties and methods using the hash prefix the these private fields are completely hidden from outside access ensuring they can only be used within the class this prevents accidental or unauthorized access making the code more secure and easier to maintain compared to previous approaches like naming conventions or symbols which didn’t fully hide the data so your exercise is to implement private properties and methods with es 2022 in a grocery lless application in this exercise you will create a grocery list class and a grocery item class to manage a grocery list application the goal is to understand and apply the concept of abstraction by using ES 2022 private properties and methods this will help you hide the implementation details and expose only the necessary parts of these classes so let’s do a quick overview of the instructions for this exercise the first is to create the grocery item class this class should have private properties for the items name and quantity it should include a Constructor to initialize these proper properties and Implement a method to display the item details this method should be public and provide a formatted string of the items details second create the grocery list class this class should have a private property for the list of grocery items include methods to add an item to the list remove an item from the list by name and display all items in the list and ensure that the internal list of items is not directly accessible from outside the class now the third instruction is using es2020 to private properties and methods use the hash prefix to Define private properties and methods in both classes ensure that no implementation details are exposed outside the class so the example code here is the starting point for the grocery item in grocery list classes so we’ll create a grocery item class so we have a Constructor which takes in the name and the quantity now it will have a public method to display item details so I’ll name this display item now let’s create our grocery list class and I’ll scroll up so we can see it better so this will have a Constructor it will have a public method to add an item to the list so we name that add item and that takes in name and quantity we have a public method to remove an item from the list by name can name that remove item pass in the name as the parameter and a public method to display all items in the list name that display list so this is this is our starting point code so now the task checklist first Define the grocery item class create private properties name and quantity implement the Constructor to initialize these properties and implement the display item method to return a formatted string of the items details task number two Define the grocery list class create a private property items to hold the list of grocery item objects implement the ad item method add a new grocery item to the list implement the remove item method to remove an item by name implement the display list method to display all items in the list the third task is to test the classes create an instance of grocery list add multiple items to the list display the list to ensure items are added correctly remove an item and display the list again to ensure the item is removed correctly by completing this exercise you will gain hands-on experience with es 2022 private property and methods enhancing your understanding of abstraction and encapsulation in JavaScript so now for our grocery item let’s declare our private properties which is name and quantity now we will set these prate properties so this as name is set a name and this quantity is assigned to quantity now now to display the items we can log and actually I will have it return the value rather than log so I use back ticks and I can say item this and then hash name and then quantity this quantity so we’ve implemented that class let’s expand this so you can see a it better let’s scroll now we want to create a private property for our list of grocery items so we’ll name the items and we The Constructor is where we will initialize this array so this items assign to an empty array I’ll scroll that so for adding an item I will create a new grocery item object so item new grocery item passing in the name and the quantity so now I will push to the end of the array so item push adding that new item so now for the remove method say this items is assigned to this. items we use the filter method we pass in a callback function this is a predicate so the item. display item so that output here which includes the name and the quantity so if that includes I’ll use back tick item and then the name then in that case it would be filtered out in the case when it is not included and now to display everything I can say return this items. map then pass in our call back item display item and I can say do join and we’ll specify a new line so all the items will be displayed on their own line so now let’s resizes so we can see our console so now we want to create a new instance of the grocery list new grocery list grocery list let’s add some items so do add item so I’ll say apples the quantity of five and I’ll do shift option down arrow so to add bananas and we’ll specify the quantity to be three then we can call log grocery list dot display list let’s save that so here we see the expected output so it’s calling the display item method for each of them so now let’s remove an item so I can say grocery list. remove item so remove apples and then let’s copy this and we will call it again so now let’s say if I clear it and we run it again we see for the first output is apples and bananas and after we call the remove method it successfully just displays what is left in our grocery list which is bananas weak map provides a way to securely store private data for an object without preventing garbage collection when the object itself is no longer in use here’s how you can use weak map to implement private properties and methods within the programmer class so let’s define underscore language and instantiate a new week map and consor work new week map so this data type allows it to store key value pairs so now we will create a programmer class The Constructor will take in a name and a language so now we can set the name to be a public property but in this case we want the language to be private I’ll just add a comment here to better describe what we’re doing so store language in a week map with this as the key so I can set underscore language do set so here we are set in the week map so for the first argument we specify the object so in this case it would be the this keyword which refers to this current programmer object and we will specify the value being language right so the value that we pass in to the Constructor so now let’s store a private method in a week map so underscore work right this week map that we created up here we will set the this keyword referring to this current object and for the value we would specify a callback function So within it we will log use back ticks this.name is coding in do the weak map which is named uncore language. getet and the this keyword as its key so now we can save that so now let’s Implement a method named code so this is a public method and this will call the private method that we have stored in the weak map so I add a comment access and invoke the private method so underscore work which is the name of that week map call the get method and we pass in the this keyword so this current object which is the key and now we need to call or invoke this method so open and closing parentheses to call that method so now let’s create instance of this programmer class so I’ll say cons programmer new programmer with my name as Steven and the language of JavaScript and let’s call that public method code and we save that we see Steven is coding in JavaScript so we call the code method we this call the method defined in our weakmap which is a private method so let’s go over a discussion of the week map data structure and the benefits in usage so first is garbage collection A major benefit of using weak map is its handling of keys if there are no other references to a key object in this case an instance of programmer it can be garbage collected this helps prevent memory leaks and applications where objects are dynamically created and destroyed the second benefit is encapsulation using weakmap for storing private data ensures that these details are not accessible from outside the class this is much more secure than using properties prefixed with an underscore as these are only conventionally private third is Arrow functions and the this keyword Arrow functions do not have their own this keyword contexts instead they inherit the this keyword from the enclosing execution context within underscore work this refers to the programmer instance allowing access to the instance’s name and other properties securely stored in the week map so let’s consider an alternative with a single week map you can also group all private properties into a single weak map entry per object though this might make the code slightly more verbose short an example of that let’s comment out this implementation we will create a new one so I’ll say cons private props new week map so now we will create a new implementation of programmer so the Constructor takes in the name and the language let’s remove that underscore so our C braces now we will say private props move this up do set so for the key it is this current object so the this keyword and for the value we will specify a JavaScript object so here we will store key value pairs so we’ll specify the name the language so now let’s specify the work method so we’ll specify a call back so we will log back tick private props doget the this keyword and the property of the name is coding in private props doget the this keyword. language so now we Implement our public method code and this will call Private props doget this keyword and calling the work method so now when we output it we get the same expected result to in conclusion using weakmap for managing private data in JavaScript classes provides a robust way to ensure encapsulation and data security this approach is particularly useful in scenarios where data privacy is crucial and helps maintain clean API boundaries within your [Music] classes how does using weakmap for private properties and methods enhance data encapsulation and Security in JavaScript classes using weakmap for private properties and methods enhances data encapsulation and security by ensuring that private data is not directly accessible from outside the class this keeps the implementation details hidden providing a secure way to manage private data within objects what are the benefits of using weakmap in terms of garbage collection and how does this prevent memory leaks in JavaScript applications weak map allows objects to be garbage collected when there are no other references to them even if they have private data stored in the week map this helps prevent memory leaks by ensuring that memory used by objects no longer in use is freed up automatically what distinguishes week map from the es 2022 hash Syntax for private properties and methods and why might you choose to use week map weak map allows you to to store private data for objects without preventing their garbage collection when they’re no longer in use making it useful for managing memory efficiently the es 2022 hash syntax provides built-in support for private properties and methods making them truly private and not accessible from outside the class you might use weak map if you need private data that can be automatically cleaned up by garbage collection to prevent memory [Music] leaks so we’ll start by demonstrating how to store a private property in a programmer class using a weak map and then show how to define property accessors so let’s set language to a new week map and we’ll Define a programmer class so once again we have our Constructor setting the name in the language let’s remove that underscore we’ll set the name and the language with the weak map so but this operat Ator or this keyword rather for the current object and the language so this property is public and this is private now we’ll Define a method named get language in order to access this private property with the private value which is the language so we will return language doget and then the this keyword so we’ll create a new programmer so cons programmer is assigned to new programmer Steven and the language of JavaScript so now let’s call the get language method we need to call the console log so log and then programmer doget language save that and we get the value of JavaScript so now using object. Define property to define a getter for cases where you want the property to be accessible more like a property rather than a method you can use object. defin property so rather than calling the get language method we prefer to access it through a property named language so here we can set object. Define property so the first argument is the this keyword so this current object now we will name the property so this case I’ll name it to be language and then we’ll pass in an object so use the get keyword word set this to Anonymous function and here we return language. getet and this right so we don’t need this method anymore now we can access it through notation through this property that we created so rather than doing get language you can access it with language as that is the name of the property that we specified here so now when we call it let’s clear it actually and let’s say save it we get the expected result as this is calling this function defined here cleaner es6 Syntax for Getters and Setters in es6 Getters and Setters can be defined within the class body providing a more concise and readable way to access properties so let’s delete here we Define the property and let’s define a getter so we use the get keyword and then space and then the name of the property so we’ll name it language and this return returns right so we’re using the weak map here get and then the this keyword so now let’s define a Setter so we’ll set the language the parameter will be new language let’s move this up so if new language is falsy in the case when it’s an empty string for example then we’ll throw an error saying language cannot be empty and that with the semicolon otherwise we will update the value stored in the week map so set so the key is the this keyword so this current object and we’ll update the language all right so now we can access language as if it were a property so here let’s clear this when we save it we get the expected result so now let’s update the language so I can say programmer. language and I’ll set this to a new language such as python so let’s scroll up so let’s log this out programmer. language and I save it here I see the value has been successfully updated to be python as when we set this value so programmer. language is assigned to python we are calling the setter let’s expand this and I’ll discuss it so first let’s consider the weak map which we Define here this provides a way to securely store private data associated with an instance so object. Define property this method is useful when you need to create Getters or Setters that appear like properties but are backed by methods it allows for fine grain control over property characteristics es6 Getters and Setters these provide syntactic sugar that makes accessing and modifying properties intuitive and similar to accessing traditional class properties this method is particularly useful for validation logging or handling side effects during property access in conclusion these different approaches allow JavaScript developers to encapsulate and protect data within classes effectively ensuring the implementation details are hidden and that public interfaces are clean and easy to use using these features appropriately can help maintain and scale large code bases making your code more robust and easier to manage how do es6 Getters and Setters enhance the encapsulation and control of property access within classes es6 Getters and Setters enhance encapsulation and control by allowing you to Define methods that get or set property values this provides a way to add logic when accessing or modifying properties such as validation or transformation while keeping this syntax similar to regular property access what are the benefits of using the get and set keywords in es classes compared to traditional methods for accessing and modifying properties using get and set keywords in esess classes allows for more intuitive and cleaner Syntax for accessing and modifying properties similar to regular property access they also enable adding custom logic such as validation when getting or setting a property enhancing encapsulation and [Music] control so let’s cover inheriting and extending the programmer class we’ll start with a base programmer class that has a Constructor for initializing a programmer with a name and a basic method for coding so we’ll specify our class and our Constructor except a name now we’ll just set this name property and we have a simple method for coding so this will log out do back ticks this.name starts coding so we’ve implemented our Base Class so now let’s create a derive class which would be a front-end programmer so we will extend this General base programmer class to create a front-end programmer class that includes additional properties and methods relevant to front-end programming so Implement that just below it so it would be class frontend programmer and we’ll use the special keyword extends programmer so the derived class will inherit from the base class when we use the extend keyword and this is because the front-end programmer is a programmer so this is how you would achieve inheritance using the es6 class syntax so we inherit the properties and the methods from the base class so let’s create our Constructor function this accepts the name and we’ll specify an additional parameter which will be tools so we can call Super and then name and so this keyword super this calls the super class Constructor with the name argument so we’ll call this Constructor of the base class so let me add a commment here just to better describe that I’ll say calls the super class Constructor with the name now we’ll set the tools based on the argument passed in so I’ll add a comment to describe this as well I’ll say additional property specific to frontend F camers so now we will specify its own code method so we’ll say super . code so this calls the generic code method from the programmer based class and I we add additional functionality so I’ll log out I’ll use back ticks I’ll say this. name codes with I’ll say this. tools land it with a period and a semi let me extend this so we can see it better so now we can add methods specific to a frontend programmer so I’ll say design let me scroll up so we can see now I will log out back TI this.name also designs the user interfaces so here we see our derived class frontend programmer is a more specific version of the programmer Base Class and has additional functionality so now let’s use this deriv class we create an instance of the front end program class and we’ll demonstrate the use of both inherited and specific methods so I’ll say cons front and Dev assign to a new front end programmer I’ll pass in my name and I’ll specify the react JavaScript library as the tool so let’s resize it so we can see the output and I’ll say front end Dev and we call the code method we save it so here we see Steven starts coding and Steven codes to react so that first log statement Steven starts coding is implemented in the general or the base programmer class right that is because we called super. code and then we see it outputs the log statement in the front end programmer so I resize it when it says Steven codes with react so now let’s call another method I’ll say frontend dev. design Implement that and here we see this log statement we specified here which is Steven also designs the user interfaces so let me expand this and we can discuss it so we covered inheritance so the front-end programmer class inherits from the programmer Base Class gaining access to its methods while also being able to introduce new properties and methods or override existing ones like how we did with this code method we use the keyword for super so the super keyword is essential for calling the Constructor of the base class so in this case the programmer class from the derive class it ensures that all the initialization logic in the super class is properly executed before additional setup in the subass and we covered method overwriting the code method is overwritten in in front-end programmer to extend its functionality but it also calls the superclasses code method to maintain the general coding behavior in conclusion this example clearly illustrates how to effectively use inheritance in JavaScript to create a hierarchy of classes where derived classes extend and specialize the behavior of their base classes this pattern is crucial for structuring complex applications in a way that promotes code reuse and logical organization [Music] how is the super keyword used in the front-end programmer class the super keyword in the frontend programmer class calls the Constructor of the programmer Base Class ensuring that the name property is initialized correctly before adding more Properties or methods specific to frontend programmer what are the benefits of using inheritance when extending the programmer class to create the front end programmer class using inheritance to extend the programmer class allows the front-end programmer class to reuse existing code add new properties and methods and override existing ones making the code more organized and easier to [Music] manage let’s go over method overwriting with es6 classes we will start with a base programmer class that has a generic work method then we’ll create a specialized front-end programmer class that extends programmer and overrides the work method to add specific behavior so let’s Implement our Base Class so that will be a programmer we’ll implement the Constructor to accept a name parameter so this.name is assigned to name now let’s implement the generic work method so we’ll say log and tab back tick then this.name is solving problems so this is our Base Class which we will extend so we Implement class front and programmer extends the programmer base class because the frend programmer is a programmer so this accepts and name and we call the super classes instructor so comment initialize the Base Class part of the object and we will override the work method so we’ll call super. workor so this calls the Base Class method and now we will add our own specific functionality so I’ll say log say this.n name is also designing and implementing UI components so now let’s use our derived class say cons I’ll say Steven equals new front end programmer so it accepts a name parameter so we’ll pass Steven as the argument now we’ll say steven. and we’ll save it and here we see our expected output so calls super. work so calls the Base Class implementation of the work method so we see Steven is solving problems and then we will log out Steven is also designing and implementing UI components so let’s expand this so understanding the method lookup and the super keyword so method lookup when a method is called the JavaScript engine first looks for it on the object itself if it can’t find the method it walks up the Prototype chain to find the method in the parent class so in this case frontend programmer its prototype or its parent is the programmer Base Class and able to achieve inheritance through the extends keyword so using the super keyword the super keyword is crucial in subclass methods to call corresponding methods defin in the super class this feature allows subclasses to enhance or modify the behavior methods they inherit without completely rewriting them thus promoting code reuse and reducing duplication in conclusion by overriding methods and using the super keyword effectively you can ensure that subclasses not only tailor inherited methods to their specific needs but also leverage and extend the functionality provided by the super classes this approach is beneficial for maintaining logical and maintainable code and objectoriented JavaScript applications as it minimizes redundancy and ensures a clear and efficient inheritance structure [Music] what is method overwriting in es6 JavaScript classes method overwriting in es6 jvip classes is when a subass provides a specific implementation for a method that is already defined in its parent class replacing the parents method with its own version how does method look up work when calling a method method on an object in JavaScript when calling a method on an object in JavaScript the engine first looks for the method on the object itself if it’s not found it checks the object’s prototype and continues up the Prototype chain until it finds the method or reaches the end of the chain what is the role of the super keyword in a subclass methods in JavaScript the super keyword in subclass methods and JavaScript is used to call methods from the parent class allowing the subass to build on or modify the behavior of those methods so let’s summarize what we covered in this section es6 classes we explored how es6 class syntax provides a clearer more concise way to define Constructor functions and manage inheritance classes make the the structure of object ored JavaScript cleaner and more similar to other programming languages which helps in organizing code and improving readability hoisting the concept of hoisting was discussed to understand how JavaScript interprets function declarations and variable declarations differently we noted that function declarations are hoisted to the top of their containing scope allowing them to be used before they appear in the code static methods we learned about static methods which are called in the class rather than on instances of the class these methods are useful for utility functions that operate independently of class functions the behavior of the this keyword in different context was examined especially it can vary depending on the scope and the manner in which functions are called private members using symbols the use of ESX symbols as a way to somewhat hide implementation details was covered symbols provide a way to create properties that are not easily accessible from outside the class private members using weak Maps we discuss using weak maps to securely store private data for objects providing true encapsulation by ensuring that these details are inaccessible from outside the class and are eligible for garbage collection when no longer needed Getters and Setters the implementation and benefits of Getters and Setters were explored these are used to control access to the properties of an object allowing for validation logging and other side effects when properties are access or modified inheritance we covered how classes can inherit from other classes allowing for shared Behavior or across different types of objects and reducing code redundancy method overwriting the ability to override inherited methods was demonstrated showing how subclasses can modify or extend the behavior of methods defined by their super classes this section aimed to deepen your understanding of modern JavaScript features and best practices enhancing your ability to write clean maintainable and efficient JavaScript code in a professional development [Music] environment as app grow in size and complexity managing all the code in a single file becomes impractical and hard to maintain to address this issue it’s beneficial to split the code into multiple smaller files each encapsulating a specific functionality or feature these smaller files are called modules let’s go over the benefits of modularity the first benefit is maintainability smaller modular files are easier to understand debug and test the second benefit is code reuse modules can be reused across different parts of an application or even in different projects reducing code duplication the third benefit is abstraction modules allow developers to hide implementation details while exposing a clear interface making it easier to interact with the code practical implementation imagine you have a programmer class and its related functionalities divided across multiple modules for better organization you would place the programmer base class in its own file and for example the frontend program class in a separate file as these classes grow and gain more methods and enhance functionality managing them becomes easier since each class is in its own file or in other words its own module module systems in JavaScript historically JavaScript did not support modules natively and various Solutions were developed one of them being AMD which stands for a synchronous module definition this was primarily used in browsers and this format allows modules to be loaded asynchronously another module system is commonjs this is used in node.js and this format is designed for server side development another module system is UMD which stands for Universal module definition this combines the approaches of AMD and commonjs making modules usable in both the browser and node.js environments es6 modules with the introduction of es6 javasript now natively supports modules in the browser this system uses Import and Export statements to handle dependencies this course will cover commonjs for serers side applications and ESX modules for browser based JavaScript providing you with the skills to work flexibly with JavaScript in multiple environments in conclusion understanding and using modules and JavaScript not only improves the structure and maintainability of your code but also enhances its scalability and reusability by adopting modern JavaScript module standards like es6 modules and commonjs you ensure that your applications are robust maintainable and ready for growth what are the key benefits of using modularity in JavaScript applications and how do modules improve maintainability reuse and abstraction the key benefits of using modularity and JavaScript applications include maintainability this leads to smaller modular files that are easier to understand debug and test the second benefit is code reuse modules can be reused across different parts of an application or in different projects reducing code duplication the third benefit is abstraction modules allow developers to hide implementation details while exposing a clear interface making it easier to interact with The Code by organizing code into modules you make the application more manageable enhance its scalability and improve overall code quality how do commonjs and es6 modules differ and why is it important to understand both for developing JavaScript applications in various environments commonjs and es6 modules differ primarily in their usage and syntax with commonjs it is used in node.js for serers side development and it uses the require function to import modules and module. exort to export them with es6 modules this is supported natively in browsers and it uses Import and Export statements to manage dependencies understanding both is important because it allows you to work flexibly across different JavaScript environments using commonjs for Server applications and es6 modules for browser based applications ensuring compatibility and leveraging the strength of each module [Music] system modularity is a fundamental Concept in software architecture that helps organize code in a way that enhances maintainability reusability and scalability let’s apply these principles using the programmer class in a node.js environment so let’s consider the principle of cohesion cohesion refers to how closely related and focused the responsibilities of a single module are high cohesion within modules often leads to better code maintainability and understanding in the context of node.js you can create a module for the programmer class so each module and node.js has its own scope and anything defined in the module is private unless it is explicitly exported so let’s create new folder and I’ll name this undor nodejs now within it I’ll create a new file and I’ll name this programmer. JS So within it I can Define the programmer class so I’ll say class programmer Define my Constructor function so it takes in a name and the preferred language of the programmer so I’ll say this.n name and this. language now Implement a simple method for code which is just console log I’ll say this.name is programming in this. language and that with a period so now this class is only accessible within this file so within this module so we want to export it so a comment export the programmer class as the modules default export so in order to make this class available in other files I can say module. exports and will assign it to the programmer class so by doing this this makes this class the default export now I could also put it inside a JavaScript object and by doing this it now becomes a named export rather than a default export so I’ll undo that with command Z so now using the programmer module in another file I’ll create index.js and I want to utilize the programmer class in this file so I need to import that so I can do cons programmer and I will use the buil-in require function and pass in a relative path to where the programmer class is or the programmer module is so be4 slash meaning the current directory and the name of the file which will be program I can end that with a semicolon so now I can create an instance of a programmer so I can say const I’ll say Steven equals new programmer passing in my name and the preferred language of JavaScript and I can call step. code so the importation here utilizes the require function provided by Common JS in nodejs so nodejs refers to serers side environments so let’s bring up the integrated terminal and I’ll navigate to node.js and I will run the index file so node index.js and here we see outputs what we expected as the console statement so I log here the console statement defined in the code method so this was achieved through a default export now if I were to use a named export right so I put it inside a JavaScript object and save that in order to utilize this I would need to destructure it put it within curly braces now if I bring up the integrated terminal up arrow and run it again we get the expected result but in this case since we are just exporting one class it makes more sense to make it a default exporter clean this up the command D so encapsulation and privacy by structuring your application into modules and only exporting what is necessary you enhance encapsulation for example if there were private methods or properties within the programmer class these would not be accessible to Consumers of the programmer module who only receive what is explicitly exported so the encapsulation ensures that only the intended public interface of the programmer class is exposed and use in inclusion this lesson highlights the importance of modularity in software development particularly in node.js using commonjs modules by organizing code into cohesive modules and properly managing exports developers can create maintainable reusable and scalable applications the modular approach not only supports good software design principles but also ensures that each part of the application can evolve independently why is H cohesion important in software modules and how does it contribute to the maintainability and understandability of the code High cohesion in software modules means that the functions and responsibilities within a module are closely related and focus on a specific task this is important for two main reasons the first being maintainability modules with high cohesion are easier to update and debug since changes are localized to specific area with related functionality this reduces the risk of introducing errors elsewhere in the system the second reason is understandability high cohesion makes the code more intuitive and easier to understand when a module has a single well-defined purpose developers can quickly grasp what it does and how it works without needing to sift through unrelated code in summary High cohesion leads to more organized manageable and comprehensible code making the development process smoother and more efficient explain the concept concept of encapsulation in the context of modular programming how does using modules and node.js enhance encapsulation and what are the benefits of this approach encapsulation and modular programming refers to the practice of keeping a module’s internal details private and only exposing a limited necessary interface to other parts of the application and node.js using modules enhances encapsulation by scope isolation each module has its own scope meaning its variables and functions are not accessible outside unless explicitly exported by only exporting necessary parts of a module you control what other parts of the application can interact with reducing the risk of unintended interference and misuse now there are three main benefits the first is improv security sensitive or complex logic is hidden preventing unauthorized access and potential misuse the second benefit is the ease of Maintenance encapsulated modules can be updated or refactored independently without affecting other parts of the application and the third benefit is clear interfaces while defined interfaces make the system easier to understand and use promoting better code organization and collaboration in summary encapsulation via modules and no. JS leads to safer more maintainable and better organized code what is the Syntax for exporting a class or function as the default export in a commonjs module and how do you import and use this default ort in another file in commonjs to export a class or function as the default export you use module. exports to import and use this default export in another file you use the require [Music] function so for your exercise create a file named grocery item. JS and Implement a grocery item class with the properties of name and quantity then Implement a display method export that file or module and utilize it in index.js so for your exercise here in the node.js directory I’ll create a file and I’ll name it grocery item. JS So within it I’ll implement this class so it’s class grocery item then our Constructor so it’ll take in a name and quantity so I’ll assign these properties for the name and for the quantity and then we’ll have a display method so log and then tab back tick so I’ll say the interpolation of this.name times this. quantity so I implemented this simple class and now I want to export it so that I can import this class and utilize it elsewhere so module. exorts and I’ll make it a default export assign this to the grocer item class and so this enables me to import and utilize this class in other files so in the same directory I will create a file index.js and I will use the commonjs syntax to import it so I’ll say and the name of that export is grocery item assign to and I use the buil-in require function in commonjs and the directory is grocery item so now I can utilize this class grocery item as if it was defined in this file so I can say cons item new grocery item so the first parameter it accepts is name so I’ll say Apple apples as the the argument and for the quantity I’ll say four so now I want to call item. display let’s bring up the integrated terminal so I’ll do command J it’ll be control J on Windows and I will navigate to this file so I’ll run node index.js and here I get the expected output so let’s cover modularizing the programmer class using es6 modules in the previous lesson we use commonjs modules in order to Import and Export modules in serers side environments using node.js so with es6 modules this provides a modern and cleaner syntax in order to achieve the same thing for JavaScript files that run in web browsers so consider the scenario we want to ensure that certain properties of our programmer class such as skills are kept private and managed through a weak map we’ll separate the concerns into two modes one for the week map and the other for the programmer class itself so here in our directory _ practice I’ll create a new file and I’ll name this programmer skills. JS so this module will maintain a weak map to store private data related to programmers so let’s create that week map structure so programmer skills is assigned to a new week map so now we’ll create a function so I’ll name the set skills this will accept two parameters so a programmer object and the skills and we will just update the week map so it be programmer skills. set so the first parameter that we need to pass is the key so that would be the programmer object or instance and then the value so that will be the skills so now we’ll create another function for retrieving the value so we’ll name this get skills this accepts one parameter which will be the programmer and we’ll use that as the key in order to return the value so programmer skills. getet and then programmer as the argument so these functions are only available within this file so if we were to use commonjs syntax in order to export these two functions so we can use it elsewhere in our program we need to do module. exorts then a JavaScript object and specify set skills and get skills but with es6 modules we have a cleaner syntax to accomplish the same thing so we can remove this and just use the export statement so now both these functions are available to be used in other files so let’s create another file in our undor practice directory and I’ll name this programmer. JS so this module defines the programmer class and imports the functionality from programmer skills to manage skills privately so we use es6 module syntax to import those two functions so I’ll use the keyword of import and then curly braces set skills and get skills now we use curly braces because we are destructuring it so we use the from keyword and then we’ll specify the path to the file so it’s for slash for the current directory and then programmer skills. JS so now we can utilize these two functions in our class so it’ll be class programmer we’ll Define our Constructor function this accepts two parameters so the name and the skills so now let’s assign the name property and let’s utilize that function in order to set the skills and manage it privately so the first argument will be the this keyword meaning this current programmer object and the value will be these skills so let’s define another method I’ll name this code so this will log so Tab and then back ticks this.name is coding in then we’ll utilize the get skills function that we imported and pass into this keyword so this current programmer object so once again we will use the export keyword which is provided in es6 modules and we’ll utilize this in our index.js file so once again we use our import statement import the programmer from programmer. JS so let’s create an instance of this object I’ll say Dev new programmer the name of Steven and the skills of JavaScript so now we will call the code method so now in order to utilize ESX modules and have it executed in our web browser we need to update this script tag so instead of the type being text/javascript we’ll update this to be module so it’s treated as es6 module so let’s start live server so we’ll bring up the command pet with command shift andp then it’s live server open with live server and then we can inspect let’s go to our console and let’s resize this so here we see our expected output when we call the code method which is Steven is coding in JavaScript so another thing I want to show here in our program rjs file we exported our programmer class but we could also make this a default export so rather than using the export statement here I’ll remove that and I can say export default programmer so now when we go to our index.js file because it is a default export I can remove the curly braces and save it let’s see our output and here we see actually let’s clear against just so make it more easily viewable I can save it again and I get our expected output so this shows how we can use es6 modules in order to organize our code so as our applications grow in size we want to split up our functionality into different files so let’s cover some key points the first is modularity and privacy by separating the programmer class and its skills management into different modules we keep implementation details hidden and only expose what is necessary through exports es6 modules using Import and Export statements we can clearly Define dependencies and how modules interact this approach is cleaner and more maintainable than older module systems webpack and browser modules while modern browsers understand es6 modules natively complex applications might benefit from tools like webpack for abundantly modules managing dependencies and optimizing load times in conclusion this setup illust rates how to effectively use JavaScript modules to encapsulate logic manage privacy and expose a clean public API this modular approach not only AIDS in code organization but also enhances security and scalability and web development [Music] projects how do es6 modules enhance code maintainability and organization compared to older module systems es6 modules improve maintainability by providing a clear structure for defining and managing dependencies with Import and Export statements this helps keep the code organized and easier to manage what are the benefits of using tools like weback in conjunction with es6 modules for modern web development using tools like webpack with es6 modules helps bundle and optimize code managing dependencies more efficiently this improves load times and ensures that all necessary modules are correctly included making the development process smoother and the application [Music] faster so for your exercise use the es6 module syntax and create a file named grocery item. JS and Implement a grocery item class with the properties of name and quantity then Implement a display method export that file and utilize it in index.js so you imp imped this exercise previously and you use the commonjs module syntax in a node.js environment but in this case you implement these files and utilize it in a web browser so to implement this in the directory undor practice is where I have my index HTML file so I’ll create a new file grocery item. JS so I didn’t implement this in the previous lesson so to help us save time I’ll just copy this and I’ll paste it in here but currently I’m using the commonjs syntax but instead I want to use the es6 module syntax so I’ll make the grocery item class a default export so I can do that with export default and then grocery item so now I can import this in my index.js file so I’ll use the keyword import and then grocery item from grocery item. JS so now let’s create a new item equals new grocery item of bananas bananas and a quantity of five then I will call item. display and I will save it let’s resize this so we can see the web browser close the sidebar with command B and here I see the expected output of bananas times 5 in the landscape of modern JavaScript development especially when building browser applications the roles of transpilers and bundlers are crucial these tools help manage and adapt code for various environments ensuring compatibility and efficiency trans filers a trans filer is a type of tool that transforms source code written in one program language or version like modern JavaScript es6 into another version they may be more compatible with current environments such as older JavaScript es5 the old browsers can understand a popular transpiler is Babel one of the most widely used transpilers it allows developers to write modern JavaScript while ensuring that the code runs smoothly in environments that only support older standards for instance features like classes the let keyword the cons keyword Arrow functions and template literals introduced in es6 are not universally supported in older browsers so suppose you have a programmer class defined with modern JavaScript features using Babel this can be transpiled to be compatible with environments that do not support the latest JavaScript syntax now let’s consider bundlers a bundler Aggregates all the modules in your project and sometimes their dependencies into a single file or a few files this process is crucial for optimizing load times and managing resources efficiently a popular bundler is webpack webpack is the most popular bundler in the modern web development toolkit webpack not only bundles files but also minifies code and provides optimization like tree shaking which refers to removing unused code so an example with webpack you can configure webpack to bundle your JavaScript modules including the programmer class module into a single file this bundled file is then included in your web application ensuring that all script dependencies are resolved and manage efficiently so why would you use these tools well one reason is compatibility it ensures that modern code Works in environments that are not up to date with the latest ecmascript standards the second reason is performance it reduces the size of the code and the number of server requests required to load your application and third is for development efficiency it simplifies development by allowing you to use modern JavaScript features without worrying about browser compatibility while these tools are essential for browser applications due to their varied support for JavaScript standards across browsers nodejs environments generally do not require such tools for running JavaScript code AS no. JS is typically up to date with the latest JavaScript features however bundlers like webpack might still be used in nodejs applications for optimizing the application deployment in conclusion understanding and utilizing transpilers like Babble and bundlers like webpack is essential for any modern web developer looking to create efficient maintainable and compatible web applications they are especially important when the application needs to be scaled or maintain across different browser environments what is the primary function of a transpiler in modern javascrip development and why is it important the primary function of a transpiler in modern JavaScript development is to convert code written into newer versions of JavaScript like es6 plus into older versions like es5 that is compatible with a wider range of environments including older browsers this is important because it ensures that modern JavaScript features can be used by developers without worrying about compatibility issues allowing the code to run smoothly across all browsers how does bble help in making modern JavaScript features compatible with older browsers Babble helps make modern JavaScript features compatible with older browsers by converting newer JavaScript syntax and features like classes the let keyword the cons keyword and arrow functions into older syntax the all browsers can understand this process called transpiling ensures that code written with the latest JavaScript standards can run on any browser regardless of its version what role does a bundler like webpack play an optimizing web application performance and Resource Management a bundler like webpack optimizes web application performance and resource management by combining all your JavaScript modules and their dependencies into a single file or a few files it also minifies the code and removes unused Parts by utilizing tree shaking which reduces the file size and the number of server requests needed to load the application this leads to faster load times and more efficient resource usage why might nodejs applications generally not require transpilers like Babble but still benefit from using bundlers like webpack node.js applications generally do not require transpilers like Babel because node.js often supports the latest JavaScript features however it can still benefit from using bundlers like webpack to optimize performance by combining multiple files into one reducing file size through minification and managing dependencies more efficiently this makes the application faster and easier to deploy so let’s set up our JavaScript development environment so first we will cover installing essential tools with mpm before you start ensure that nodejs is installed on your machine as it comes with mpm which stands for node package manager this tool is crucial for managing ing third party libraries and development tools with mpm we can install open source packages to utilize in our projects so let’s open up the integrated terminal I can do that with command J or control J from Windows so ensure that no JS is properly installed by checking its version in the terminal I can do that with node DV and here I see I have version 20.1 16.0 so now let’s create a new directory for our project and we will navigate to it so rather than clicking on this icon I can just do that through the command line so I’ll do mkd for making a new directory and I’ll name it es6 actually I’ll name it underscore es6 hyphen tooling now I specified the underscore so that this directory shows up first when I view my project files in vs code so now let’s change directory into that new folder that we created so now we will create a package.json file so first let’s cover what Json is Json stands for JavaScript object notation and it is a lightweight data interchange format that is easy for us to read and write and easy for machines to parse and generate it is often used to transmit data between a server and web applications serving as an alternative to XML XML standing for extensible markup language so J Json is a more modern way to do this Json data is structured as key value pairs within curly braces and supports nested objects and arrays so let’s run the following command to create a package.json file in this new directory that we created and this file will help us manage all of our projects dependencies and other configuration so I’ll run mpm and then the keyword in it and then D- yes to accept all the default settings so after I run this this creates a new file named package.json to help manage by mpm dependencies so I can close this so here I see it is just a JavaScript object containing properties so now let’s focus on setting up Babble so this is to transpile Modern JavaScript and es6 plus to Backward Compatible JavaScript like es5 and we will use Babble to accomplish this so let’s clear this out so step one is is we want to install the necessary Babel packages you could also reference the documentation at Babel SL usage so now let’s install the necessary Babel packages using mpm these include Babel CLI Babel core and a preset package Babel preset environment which includes all the latest ecmascript features so we can do that with mpm install then app at Babble SL CLI then at Babble SL at Babble slash preset environment and we will specify a flag for Save Dev so it’s two hyphens save hyphen and then Dev and so what this does is that this installs the packages as developer dependencies so let’s discuss what these packages stand for so Babel CLI this provides the Babel command line interface for running Babel from the command line so Babel core this contains the core functionality of the Babel transpiler and Babel preset

environment this includes plugins to enable Transformations for all modern JavaScript features so let’s run this so our packages have been installed successfully so I’ll do command K to clear this and then command D to close it and here we see our three developer dependencies have been installed and they are now listed in our package Json file so now we need to configure Babble so we want to update our scripts here so our scripts determine different command line scripts that we can run so I’ll add comma and I will name this script Babble so the value will be what command we want to run which will be Babble then index.js which will be our project file and we’ll specify the output with- o and it will be in the build directory SL index.js so let’s create a build directory in here so it be build and let’s create another file index.js so here we replace our es6 JavaScript and after transpiling it the result will be stored in the build directory so we also need to add a file and it will be period Babel RC so if you’re fixing it with a period this means that this is a hidden file so Babel RC is a configuration file used by Babel which is a JavaScript compiler to specify options and presets for transforming your JavaScript code the name Babel RC stands for Babble resource configuration so we just Define this object here so the key will be presets and the value will be an array with the string add babble /pret environment we can save that so let’s go back to our index.js file and let’s write code es6 which uses modern features so I’ll specify a class and I’ll name it programmer I’ll Define a public field so I’ll say the role of the programmer and we just assign this to developer that will Define a private field this is a modern syntax and I’ll name it experience so now let’s define our Constructor function this takes in the name this takes in the technology they work with and I’ll say experience so we will set the name we can set the technology they work with and let’s set the private field of experience so assign this to experience let’s fine I’ll close the sidebar so we can see the code better so command B I’ll name it develop and then this will log out back tick this.name develops software using this. technology with this. experience this is actually a private so I need to pass for it years of experience so we can save that and I have another method which is get experience for accessing this private field and this will return this uh experience and also we will export it so we use that export keyword so here we see this class is using the modern features of having a private field but this language feature is not supported in JavaScript es5 so that’s why we need Babble to transpile this index JS file to es5 syntax so let’s navigate again to our package Json and we have the script that we Define and so we can execute this from the command line and it will run this command specified here as the value so let’s bring up with command J or control J and I’ll run mpm run and then the name of the script which is Babel so here in our output if we view the build directory the result of transpiling this modern es6 code can be found here and this is the result of using Babble so this code is now usable for browsers that only support older versions of JavaScript so now let’s cover integrating webpack for more efficient builds while B is excellent for single files webpack is more suitable when your project consists of multiple files as it bundles all your Project’s JavaScript into one or few files webpack will Minify both your code and the final bundles to reduce file sizes minifying JavaScript code involves removing unnecessary characters like spaces comments and line breaks to reduce file size and improve load times without changing its functionality so step one for setting up webpack you will install webpack and configure it to work with Babble to handle the entire project not just individual files and second we can automate with mpm scripts so we now navigate back to package.json we will update package.json to include a script that runs webpack ensuring all your JavaScript files are processed through Babel and bundled correctly we will cover this in the next lesson so in conclusion by following these steps you set up a modern JavaScript development environment capable of handling es6 plus syntax and producing code compatible with older browsers this setup ensures that your development process is efficient and your applications are robust and maintainable [Music] what command do you use to initialize a new mpm project and what file does it create to initialize a new mpm project use the command mpm in it– yes this command creates a file named package.json which manages your Project’s dependencies and configuration why is Babel use in a JavaScript development environment and what does it transform Babble was used in a JavaScript development environment to convert modern JavaScript code so this refers to es6 and newer into an older version so this is es5 that can run in any browser this ensures that new features and syntax can be used without worrying about browser compatibility what is the purpose of the Babel RC file and how is it typically structured the purpose of the babble RC file is to configure Babel specifying how JavaScript code should be transformed it is structured in Json format and usually contains an object with properties like presets and plugins that Define which transformations to apply webpack is a powerful tool that bundles JavaScript files into a single file optimizing load times and simplifying deployments webpack is a very large topic and it’s a very configurable technology so this course lesson will just scratch the surface of his capabilities so that you are familiar with it and you can explore the documentation at web pack.jpg file or a smaller amount of files so Babel on the other hand transpiles modern JavaScript so es 2015 or newer into backwards compatible versions so that our code can successfully run on older browsers and while in development we can still utilize the newest language features in syntax of modern JavaScript so let’s continue with the project that we were working on in our previous lesson let’s bring up the integrated terminal with command J or control J and we’ll run MC TM install and we’ll install the package of webpack webpack CLI Val loader will specify the flag of save Dev and– Legacy pure dependency SS package web pack is a powerful module bundler for JavaScript applications it takes modules with dependencies and generates static assets representing those modules so webpack CLI this is a command L interface for webpack it provides commands to initialize run and configure webpack from the terminal so this package Babel loader this is a webpack loader that allows Babel to transpile JavaScript files it converts modern JavaScript code so es6 and newer into backwards compatible versions so es5 using Babble in this flag Legacy period dependencies this tells mpm to use an older algorithm for resolving peer dependencies which can help bypass conflict so we’ll install this so successfully installed we can view our package.json and here we see these packages have been added to our developer dependencies so now let’s create a webpack doc config.js file so we’re going to right click webpack doc config.js so it is not mandatory to provide a custom configuration file for webpack as it does have a default convention before this course we’ll create a simple configuration file so we want to use the commonjs module syntax to import a library so that’s path require and then path and then we would do module. exorts assign this to a JavaScript object and here we will Define our configuration so we can specify the mode so for now it’s just development we’ll Define the entry point of our application so we’ll say that is in source and then index.js and we will Define the output so after webpack bundles everything where will it Place those files so we’ll specify the path and here we will use this path that we imported and so what this will do is this will create an absolute file path to where we want the output to be so there’s a keyword so that’s two underscores and directory name and we’ll specify the name of the directory to be disc for distribution so with this configuration we’re basically telling weback after you bundle all of our files and Minify our code Place everything in a directory named disc and we’ll specify the file name of the output and OB be main.js so now we use module we will Define some rules because we want to utilize Babel so this actually an array let’s update that so now it’s the object and then test so it’s a regular expression of for slash 10 back SL period to escape it JS a dollar sign and then another forward slash so basically we’re telling webpack every JavaScript file or every file that ends with the JavaScript extension we can say exclude node modules so the node modules directory so we don’t want to include the dependencies and we can say use and we want to utilize Babel to transpile our es6 code into backwards compatible es5 code so we can save this so this is our custom configuration don’t worry about memorizing all this this is just to demonstrate what web pack is so you have more insight so here we Define the entry point of our application to be in the source directory in the index.js file but currently our index.js file is at the root of the project so let’s create a new directory and I’ll name it source and this will contain our source code so I will copy this into that directory so I’m going instance of this programmer class so I’m going to say cons Dev new programmer say the name of Steven the technology of JavaScript and the experience I’ll say 10 and I will call the develop method now let’s go to our package Json file we wanted to find another script so that we can utilize web pack so I will name the key to be build and the value to be webpack so last thing I want to do is I want to create an index HTML file so index.html at the root of the project so exclamation point and then tab and I just want to create a simple H1 tag and I’ll say using web Haack I also want to specify a script tag so this will be in the distribution directory and the output will be main.js so now let’s bring up the integrated terminal with command and J and I’ll clear this out so we want to run our build script so we’re going to run webpack so mpm run build so webpack successfully bundled our code for our very simple project so here we specified our output directory to be disc for distribution and so this is the output that webpack generated to create backwards compatible code so once again it’s because this modern synex that we use is not compatible with older web browsers so we use Babel to trans file our code into es5 syntax and so webpack is used to bundle our code for production so this is a really simple example because we just have one file but you can imagine as our projects grow and we have hundreds of JavaScript files then weback comes a mandatory tool to optimize your code for production so here we can see what was generated now I can also update this so if I go to the webpack configuration file I specifi the mode to be development let’s change this to be production and I’ll bring up integrated terminal and let’s run the build command again so here we see the code has been minified so everything is placed on one line and all theace es and new lines have been removed to make the file size as small as possible this will help make our application faster once it’s running in a web browser so we can see this in action and actually see this in a browser so I’ll resize this and let’s open up the integrated terminal and I’ll do open and then period so this will open up finder on my Mac so now I’ll drag my index HTML file and drag it to my browser so let’s close this out so here in our index HTML file I have the H1 tag saying using webpack so we see that here and in our script tag this is referencing the production code that webpack and babble generated for us so this code and so the code that we were using in development was utilizing the programmer class with modern es6 syntax I created an instance of the programmer and called the develop method so it logged this out let’s check that it did that in our browser I can bring that up with doing the developer tools we drag that over here in our console we get our expected log statement view our sources and here we see the production code that webpack generated for us so I can close this so this is a very quick and brief overview of webpack just so you have a better understanding of what it does so in conclusion using webpack and babble together simplifies the process of modern JavaScript development by bundling and transpiling your code this stream line setup ensures compatibility across browsers and improves developer efficiency so for more detailed and advanced configuration refer to the webpack documentation at web [Music] pack.jpg and maintain code by breaking it into manag ible reusable pieces we covered commonjs so we explore commonjs which is a standard for modularizing JavaScript that allows the encapsulation of functionality into reusable packages which has been widely used in nodejs es6 modules this section covered es6 modules a native JavaScript feature that supports static Import and Export of code offering a more integrated and optimized way to handle modules directly in the browser or in node.js environments es6 tooling this topic address various tools and technologies that support es6 development enhancing code compatibility across different browsers and environments Babel we discuss Babel a JavaScript compiler that allows developers to write modern JavaScript code that is then transpiled into Backward Compatible versions for better support across all platforms webpack the lesson on webpack provided insights into how this powerful tool bundles JavaScript files and dependencies into a single file improving s speed and efficiency each topic was designed to equip you with the necessary skills to effectively use modern JavaScript tools and practices streamlining your development process and ensuring your projects are robust and [Music] maintainable node.js is an open- Source cross-platform runtime environment that enables the execution of JavaScript outside of a web browser it’s primarily used for building servers set applications and networking tools node.js supports the development of back-end Services commonly known as apis this stands for application programming interface these are essential for powering client applications such as web and mobile apps so key features of node.js one of the key features is its versatility and backend development node.js is suited for creating highly scalable data intensive and realtime applications its non-blocking event driven architecture allows it to handle numerous simultaneous connections with high throughput making an excellent choice for developing services like chat applications and online gaming servers a second feature is that it is quick to start and agile friendly nodejs is known for its ease of use and minimal setup enabling developers to quickly start building applications this attribute aligns well with Agile development practices where time to Market and adaptability are critical another feature is real word usage prominent companies such as PayPal Uber Netflix and Walmart leverage no. JS in their production environments these organizations have reported benefits such as reduceed development time decrease number of code lines and files which in turn contribute to enhanced performance in terms of request handling and response times another feature of node.js is that it enables you to use JavaScript for your backend and front end this allows developers to use the same language for both server side and client side scripts promoting skill reuse and reducing the learning curve for new Developers it provides a uniform programming language across the stack which leads to a clearer and more consistent code base njs also has a rich ecosystem nodejs benefits from a vast ecosystem of open- source libraries available through mpm which stands for node package manager which simplifies the addition of functionalities and accelerates the development process in conclusion nodejs is a popular choice for developers looking to build efficient and scalable web applications its ability to run JavaScript on the server side along with its robust tooling and supportive Community makes it a dependable and practical choice for modern web development what is node.js node.js is a runtime environment for executing JavaScript outside of a web [Music] browser so let’s go over understanding runtime environments a runtime environment is a setting where programs are executed it provides built-in libraries and manages the program’s execution offering various services such as handling IO or network request so JavaScript and web browsers historically JavaScript was primarily used within web browsers each browser comes with its own JavaScript engine which interprets and executes JavaScript code so Microsoft Edge uses the chakra engine the Firefox browser uses the spider monkey engine and Google Chrome uses uses the V8 engine these different engines can lead to variations in JavaScript Behavior across browsers within a browser JavaScript interacts with the document object model otherwise known as the Dom to manipulate web pages using methods like document. element by ID with the ID being root for this example the evolution to nodejs in 2009 Ryan do the creator of nodejs proposed an Innovative idea which was enabling JavaScript to run outside the web browser he leveraged Google Chrome’s V8 engine known for its speed and embedded it within a C++ program this integration birth node.js which is essentially an executable or aexe program that extends javascript’s capabilities Beyond web browsers so node.js does not have browser specific objects like the Dom because it is not intended for controlling webpage content instead it includes additional modules that provide JavaScript the ability to interact with the file system create servers handle networ protocols and more for example fs. read file can be used for reading files from the system and HTTP create server for creating a web server these functionalities demonstrate that node.js is equipped to handle backend Services making it ideal for building scalable Network applications what node.js is and is not node.js is not a programming language it uses JavaScript as its scripting language node.js is not a framework it does not impose any specific way way of organizing your project it merely provides a runtime environment with useful libraries node.js is a runtime environment it extends javascript’s reach to the server side offering tools and libraries that are not available in a browser context in conclusion nodejs revolutionized javascripts programming by expanding its scope from the client side in browsers to include serers side applications this advancement has made JavaScript a versatile powerful choice for full stack development node.js continues to thrive as a popular runtime environment due to its efficiency and the vast mpm ecosystem which provides numerous libraries and tools to enhance [Music] functionality node.js operates on a non-blocking asynchronous model which can be likened to a highly efficient restaurant service so let’s consider a restaurant analogy think of node.js like a single waiter serving multiple tables instead of waiting for one table’s meal to cook before taking another table’s order the waiter keeps taking orders and serving food as it becomes ready this demonstrates the asynchronous operations that node.js supports so now a technical explanation of this in node.js when a request is made the request is processed without blocking other operations nodejs does not wait for the database response but instead places a call back in the event Q which will be executed once the response is ready this allows the node server to handle other requests in the meantime contrasting this with synchronous operations in more traditional synchronous models like those used by Frameworks such as Ruby on Rails each request might be handled by one thread if the thread is busy it cannot take on more work this can lead to inefficiencies as other requests have to wait until free threads are available or additional Hardware resources must be provided synchronous operations have blocking Behavior in such synchronous environments a thread handling a database query will remain idle until the data is returned which is inefficient compared to nodes a synchronous approach so let’s go over the benefits of the node.js model the first benefit is efficiency node.js can handle numerous simultaneous operations on a single thread thanks to its event driven model this increases efficiency as the server can manage multiple tasks without waiting for any single task to complete the second benefit is scalability the ability to handle many requests on few threads allows node.js applications to scale effectively without requiring significant Hardware resources this is particularly beneficial for Io intensive applications such as web apis or real-time data processing and the third benefit is Resource Management nodes model promotes better resource utilization as the server remains active and non-idle even when data operations are pending let’s consider ideal use cases for nodejs node.js is well suited for applications that that require real-time data processing such as an online gaming application chat applications and live streaming services it excels in environments where the application needs to handle a large volume of short messages or commands that require low latency let’s consider the limitations of node.js node.js is less ideal for CPU intensive task for applications that require intensive data processing task such as video encoding image manipulation or large scale mathematical calculations no JS might not be the best choice its single thread in nature means CPU heavy tasks can block the entire system leading to delays and processing other concurrent operations in conclusion node.js leverages an asynchronous non-blocking model to provide efficient and scalable solutions for many modern web applications while it excels in handling iio operations it’s less suited for tasks that are heavily CPU bound understanding when and where to use node.js can help developers maximize their application perform performance and [Music] efficiency how does node js’s a synchronous non-blocking model improves server efficiency and scalability compared to traditional synchronous models no. js’s asynchronous non-blocking model improves server efficiency and scalability by allowing a single thread to handle multiple requests simultaneous L unlike traditional synchronous models where thread waits for a task like a database query to complete before moving on no JS processes requests without waiting it places task in an event queue and continues handling other operations this approach prevents idle waiting maximizes resource utilization and allows node.js servers to manage more requests with fewer Hardware resources making them highly efficient and scalable what types of applications are ideally suited for nodejs and what limitations should developers consider when choosing it for their projects node.js is ideally suited for applications that require realtime data processing and handle many simultaneous connections such as online gaming chat applications and live streaming services it excels in managing a large volume of short low latency messages however developer should consider its limitations for CPU intensive tasks like video encoding or large scale mathematical calculations no js’s single thread in nature can cause performance bottlenecks in such scenarios making it less suitable for applications requiring heavy data [Music] processing node jss module system is a powerful feature that allows developers to organize the code of large applications efficiently modules are discrete units of functionality that could be imported and used in other parts of a nodejs application or even across different nodejs applications so what are modules a module and node.js encapsulates related code into a single unit of functionality this could be anything from a library of utilities to a set of related functions that handle specific functionalities like database interactions file operations or network communications so why do we need modules modules are essential for several reasons one reason is maintainability by dividing applications into smaller manageable pieces modules make the code base easier to understand and maintain the second reason is reusability modules can be reused across different parts of an application or even in different projects which reduces code duplication and effort the third reason is namespace management using modules helps avoid Global namespace pollution by confining variables and functions within a local scope rather than cluttering the global scope so how do modules work in node.js in node.js each file is treated as a separate module node.js provides a simple and efficient way to create modules and expose them to other parts of your application so step one of creating a module you can create a module by placing the code into a separate Javascript file for example if you creating a utility module you might have a file named utility. JS so step two is exporting module contents node.js uses exports and module. exports to make functions and objects available to other files for instance if our utility. JS file contains a function to check if a number is prime you can export it like this so Implement a function I’ll name it is prime this accepts a number as a parameter so I’ll implement this if the number is less than equal to one return false if the number is equal to two return true since two is prime now if the number is divis by two then we return false let N initialize that to three we’ll take the square root of the number so don’t worry about memorizing this this is just to demonstrate so while n is less than equal to the Limit if the number is divisible by n then we know that it is not Prime so update the value by two only want to consider odd numbers otherwise it is prime so to make this function usable outside of this file or outside of this module we need to export it so we use the commonjs syntax module. exorts is prime so now let me create another file and I’ll name this index J so step three is importing a module so we use the require function to include the module in another file so I can say cons is prime then the requir function I’ll pass in a relative file path to the utility and save that utility. JS now I can utilize that and say log is prime I’ll pass the number of five let’s bring up the integrated terminal and I will run node index.js say we see the output of true because five is prime let’s do the value of six for example run it and here we see the value of false so this demonstrates how you would Implement a function export it and utilize it in another file so creating your own modules creating your own modules is as simple as writing any regular Javascript file and then using module. exports to expose parts of the module to other parts of your application you can expose objects functions or any JavaScript data structure in conclusion understanding how to effectively use the node.js module system is crucial for developing scalable and maintainable node.js applications by leveraging modules developers can create well organized modular code that enhances code quality and development [Music] efficiency how does the nodejs module system contribute to the maintainability and scalability of large applications the node.js module system contributes to maintainability and scalability by organizing code into smaller reusable units making it easier to manage understand and update individual parts of a large application without affecting the entire code base what advantages does the modular approach in node.js offer in terms of code organization and reuse across different projects the modular approach and node.js improves code organization by encapsulating functionality into separate units reducing complexity it also enhances code reuse allowing modules to be easily shared and used across different [Music] projects in nodejs Global objects are special objects that are available in all modules these objects provide essential functionality that could be access anywhere within a node.js application making them a fundamental part of the node.js runtime environment let’s cover the builtin global objects node.js comes with a set of predefined global objects that are readily available for use these objects serve various purposes from fundamental JavaScript objects to node specific objects that provide functionality unique to the nodejs environment the first one we will cover is the global object this is similar to the window object in browsers Global is the top level object in nodejs almost all other objects are either properties of this object or derived from it let’s consider the process global object this is one of the most important Global objects in node.js it provides information about and control over the current node.js process through process you can access environment information read environment variables communicate with the terminal or exit the current process the console global object this is used to print information to the standard out and standard err it acts similarly to the console object in browsers the buffer global object this is used to handle binary data directly it is built specifically for managing streams of binary data in node.js now let’s consider Global functions which consist of set immediate clear immediate set timeout clear timeout set interval and clear interval these globals are timer functions that help you schedule task to run after a specified duration or at a regular interval creating your own Global objects while node.js manages a variety of built-in globals developers can also Define their own Global variables that need to be accessible throughout the application here’s how to define and use custom Global objects and noj s Step One is defining a global object you can attach your custom Properties or objects to the global object this makes them accessible from anywhere in your nodejs application so we’ll use the global built-in object We’ll add a property and I’ll name this my config let’s assign this to a JavaScript object close it with a semicolon so we’ll add the property API URL we’ll just do a sample URL of https api. example.com we another property so at Port 3000 step two is using the global object once a property is attached to the global object it could be accessed in any module without requiring Imports or passing it explicitly so we can log this out we’ll do log and then tab for that keyboard shortcut then we’ll do global then that property we just Define which is my config API URL I’ll bring up the integrated terminal so I use the keyboard shortcut of command andj or control andj I’ve already navigated to where this file is in this directory so I’ll run node and I name this file five Global objects and here we get our expected value which is that API URL value that we added so caution when using Global objects while Global objects can be incredibly useful for sharing information across modules their use should be minimized due to the potential for creating tightly coupled components and the difficulty in tracking changes throughout the application it’s generally better to explicitly pass objects you need within modules through module exports and require statements in conclusion Global objects and node.js are powerful tools for developing applications which shared functionalities understanding both built-in and custom globals can help you effectively manage application-wide settings and maintain State across various parts of your application however limited use of globals is recommended to maintain a clean and manageable code [Music] base how to buil-in Global objects and nodejs facilitate application-wide functionality and control buil-in Global objects in node.js provide essential tools that can be accessed from anywhere in the application allowing for easy control and management of the node.js environment they enable functionalities like Process Management timing operations and handling binary data without needing to import or Define them explicitly in each module this makes them crucial for application-wide tasks and system level operations what are the potential risk of using custom Global objects and node.js and how can they be mitigated using Global objects and node.js can lead to tightly coupled code making it harder to track changes and debug issues globals are accessible everywhere so unexpected modifications can cause bugs that are difficult to trace to mitigate these issues it’s better to minimize the use of globals and and instead pass needed objects explicitly through module exports and imports this keeps the code base cleaner more modular and easier to maintain Global objects provide essential functions and variables that could be accessed from anywhere within a JavaScript environment whether in a browser or a node.js application let’s go over common Global functions the first one being console.log this is a global function that outputs to the console useful for debugging and logging application data second is set timeout this allows you to schedule a function to be executed after a specified delay this function is very handy for executing code after a pause clear timeout this is used to cancel a timeout previously established by calling set timeout set interval this schedule is a function to be run repeatedly at specified intervals this is useful for tasks like updating the UI at regular intervals clear interval this stops the repeated execution set using set interval so let’s cover Global scope in browsers in browser based JavaScript the global object is window all Global variables and functions are attached to this window object accessing globals when you declare a variable or function at the global level it’s accessible through the window object such as window. set timeout or window. message Global scope and node.js node.js does not have a window object because it does not run in a browser environment instead it uses a global object to provide a similar functionality so let’s discuss node.js globals in node.js you can access built-in modules and Global functions through the global object such as global. console.log or global. set timeout so an example of that we to do global. console.log this is a global console call and that with the semicolon now if we were to run let’s save this and execute it we get our expected console output now let’s call set timeout set timeout so the first argument to pass is a callback function so we’ll specify an errow function here so I’ll say log and then tab I’ll say this happens after a timeout now for the second argument for the set timeout Global function we specify the time in milliseconds so I’ll say a th so after 1 second we’ll execute this again we get our expected output and then after 1 second we see this console output so both of these set timeout and console.log are available globally so let’s further discuss variables and Global scope unlike in browsers if you declare a variable with the VAR keyword let keyword or cons keyword at the global level in node.js it does not attach to the global object this Behavior encapsulates the variables within the module scope avoiding unintentional conflicts so for example let’s comment this out fire do let message sign to follow world and then we log that out say global. message clear this out with command K up arrow and run it we see the value undefined so even though this message variable was defined at the global level it is not attached to the global object so it is enclosed within this file within this module so let’s cover an example using set interval and end interval so we can comment this out let’s define a function and I’ll name it update time so we’ll set the current date so new date and then we will log it out so back ticks to create a template literal I’ll say current time and then our dollar sign and curly braces now. two local daytime string so now we will WR a comment set an interval to run update time every second right so every thousand milliseconds I’ll say cons interval ID set interval and you want to call update time every second so this returns an interval ID which we will use to cancel it so we want to eventually stop the interval and we’ll do so after 5 seconds so we’ll call set timeout once again the first argument is a callback function so we’ll use our modern Arrow function syntax and after 5 Seconds we want to clear the interval to stop it and we need to pass the interval ID then we can log out interval cleared no more time updates now for the second argument we’ll pass in 5,000 for 5 seconds so let’s run this we’ll clear this out run it so shows the current time every second then after 5 Seconds we see interval cleared no more time updates so let’s discuss best practices while Global objects and functions are extremely useful you should limit their use reason being is you want to avoid polluting the global scope adding too many objects to the global scope can lead to conflicts and difficulties in maintaining the code it’s generally better to keep Global usage minimal second is you want to use local scope where possible you want to encapsulate variables and functions within a local scope such as within functions or module to avoid uned interactions and make the code easier to manage and debug in conclusion Global objects and functions are fundamental in both browser and node.js environments providing developers with powerful tools for performing common task understanding how to use these tools effectively and responsibly is crucial for developing robust [Music] applications how do Global objects differ in scope and behavior between browser based JavaScript and nodejs environments in browser based JavaScript the global object is the window object and Global variables and functions are attached to it and no. JS the global object is named Global but variables declared with the VAR keyword Le keyword or con keyword are not attached to it rather they are scoped to the module or in other words the file that they are defined in this difference helps prevent Global scope pollution at node.js making it easier to manage variables and avoid conflicts what are the best practices for using Global functions and variables in JavaScript to maintain code quality and avoid conflicts best practices for using Global functions and variables in JavaScript include minimizing their use to avoid polluting the global scope which can lead to conflict and difficult to maintain code instead encapsulate variables and functions within local Scopes such as functions or modules to keep your code organized and reduce the risk of unintended interactions this approach helps maintain code quality and makes debugging easier in JavaScript defining variables or functions directly in the globos scope is straightforward but can lead to complications and larger applications so let’s consider the global scope in browsers in a browser environment when you declare a function or a variable using the VAR keyword at the top level it is added to the global scope which means it is accessible through the window object so for example if you were to use VAR say hello and assign this to Anonymous function that logs out hello you can access it with window. say hello so that will successfully call the function now problems with global scope while convenient using the global scope can lead to several issues the first being namespace pollution the global namespace can become cluttered with too many variables and functions making it difficult to track down where specific things are defined the second problem is accidental overwriting if multiple parts of an application inadvertently use the global variable names they can overwrite each other leading to bugs that are hard to diagnose for example defining say hello in multiple files will cause the class loaded script to override all earlier definitions so for example in file one if we have VAR say hello set to Anonymous function and in file two we have a function with the same name so here if in file two if that is imported after file one then when we call say hello this will always log hello from File 2 regardless of expectations so the importance of modularity to mitigate the risk associated with global scope it’s essential to adopt modularity in your development approach so let’s cover modules and node.js in node.js every file is treated as a module and anything defined within that file is local to the module unless explicitly exported this encapsulation ensures that variables and functions do not inadvertently interfere with each other across different parts of an application the benefit is that it is private by default variables and functions are private to their module providing a clean namespace and preventing accidental interference and second is explicit exporting to make a function or variable available outside its module it must be explicitly exported adding a layer of control over what is exposed so for example in a node.js file we Define say hello assign this to an anonymous function log and then tab and we just log out hello to export it we use module. exports set to hello so we have to explicitly export it so this function can then be accessed in another file by importing it so we need to use the require function and then we can invoke it which we properly call the imported function so let’s cover the advantages of using modules the first is Clarity each module has a clear purpose in scope reducing complexity and enhancing readability the second Advantage is reusability modules can be reused across different parts of an application or even in different projects the third Advantage is maintainability changes in a module are localized impacting fewer parts of an application and thus reducing the risk of bugs in conclusion avoiding Global variables and embracing modularity is crucial in JavaScript development especially in larger applications or when working in a team environment by using modules developers can ensure their code is organized maintainable and less prone to unexpected behaviors caused by namespace pollution [Music] what challenges can arise from using the global scope in JavaScript especially in larger applications using the global scope in JavaScript can lead to several challenges and larger applications including namespace pollution where too many Global variables and functions make it hard to manage code and accidental overwriting where different parts of the appli unintentionally use these same Global names causing conflicts and bugs that are difficult to track down this can result in code that is harder to maintain and debug how does modularity in JavaScript help in maintaining clean and manageable code bases modularity and JavaScript helps maintain clean and manageable code bases by encapsulating code into self-contained units which we refer to as modules each module has its own scope reducing the risk of name collisions and accidental overrides this makes the code easier to understand debug and reuse as changes in one module are less likely to impact other parts of the application it also promotes better organization and Clarity leading to more maintainable and scalable [Music] applications so let’s go over creating and managing a module in node.js in this lesson we go through the process of creating a simple logging module in node.js this module will encapsulate all the functionality related to logging messages and can be reused in different parts of your application or even in other applications so setting up the logger module so let’s create the module file so here in this directory which I named loading a module so right click and I’ll name this logger JS so second we will add the functionality so we want to specify the functionality we want to encapsulate in this file otherwise referred to as a module con URL and assign to http my logger.log and we’ll Define a logging function we name it log the parameter it will accept will be a message so in a rle scenario you might send an HTTP request here but in our case we’re just going to log to the console and we’re going to log this message now this function as well as this constant is only accessible within this file or within this module so we want to make the module contents public so once again since variables and functions in a node.js module are private by default you need to explicitly export any data or functions you want to make available to other parts of your application so for exporting the functionality we would use module. exports to make the log function and the constant right this URL available outside the module so we would do module. exports and we can name this export log and assign this to this log function we also do module. exports do URL and set this to URL alternatively you could rename exports to provide a more intuitive interface to module consumers so rather than naming this URL we could rename this to be endpoint so let’s cover some best practices for exporting the first best practice is selective exporting in rro applications modules can contain numerous variables and functions it’s crucial to export only what is necessary to keep the module easy to use and understand this practice helps maintain a clean public interface the second best practice is the stability of the public interface the public interface of a module should be stable and not expose too many implementation details this this approach ensures that changes inside the module do not affect other parts of your application that depend on it so now let’s use the loger module I’ll create a new file in this directory and I’ll just name this index.js so here we need to import it so I’ll say const logger but I’ll name it I’ll use the requir function and I’ll use a relative path to where the logger file or logger module is and now we can call that so I’ll say logger log I’ll pass on the argument this is a message right so when we call logger.log I go back to logger JS you’re is calling this function which we exported and I’ll also log out so I’ll say log logger endpoint which is this constant that we defined and we named it endpoint when we exported it so let bring up the integrated terminal and I’ll run node index.js and we get our expected console log output so in conclusion by creating modules and node.js you encapsulate specific functionalities and expose a controlled interface to the rest of your application this modularity enhances code reuse simplifies maintenance and keeps your application organized when designing modules it’s essential to consider what should be private to maintain module inte integrity and what should be public to ensure [Music] usability what are the benefits of encapsulating functionality into modules When developing node.js applications encapsulating functionality into modules in node.js helps to organize code making it more manageable and reusable it allows developers to isolate specific functions or data reducing the risk of conflicts and making the codebase easier to maintain modules also enable better code reuse across different parts of an application or even in other projects leading to a more modular and scalable development approach how does careful management of a module’s public interface contribute to the maintainability and stability of a nodejs application careful management of a module’s public interface in node.js ensures that only necessary functions and variables are exposed keeping the internal implementation details hidden this reduces the risk of unintended interference with other parts of the application and makes it easier to update or refactor the module without breaking dependent code it contributes to the overall maintainability and ability of the application by providing a clear controlled and stable interface for other modules to interact with so let’s cover loading modules and node.js with the required function node.js uses the requir function to import modules which is a fundamental aspect of managing dependencies and modularity of your application this system differs from how scripts are loaded in your browser and is specific to the node.js environment so cover the basic usage of the requir function when you need to use functionality Define in another file or module you use require to load it so here are the steps of how it works Step One is loading a module so to load a module you pass the relative path of the Javascript file to the required function nodejs resolves the path and loads the module so for example you would have con logger this will be assigned to require and then you pass in/ logger so in this case the logger file is in the same directory or in other words the same folder node.js automatically assumes JS as the file extension if it’s not specified second is accessing exported members the requir function returns an object that represents the exported API of the module this object contains all the members that are exported from the module so if we were to do console. log and then logger this would output that function you can then use these members in your application like how we did logger.log and passing in the message best practices for using require the first best practice is using the cons keyword for requiring modules it’s a best practice to use the cons keyword as this prevents accidental reassignment of the module variable within your code which can lead to runtime errors so if we were to import that with con logger attempting to reassign a constant will result in an error helping catch mistakes during development so if we were to sign it for example to the number one this will throw an error if logger is declared with the con keyword the second best practice is utilizing tooling for code quality tools like JS hint can be used to scan your JavaScript code for potential errors and bad practices running JS hint on your code can help identify issues like improper use of variables before they cause problems at runtime so in your terminal you would run JS hint and the name of your file so in this case app.js this tool will report problems related to your usage of JavaScript potentially saving you from bugs that are difficult to diagnose exporting a single function sometimes you want to export a single function from a module rather than an object this can simplify the usage of the module where only one functionality is being provided so if we have our logger function we can do module. exports and assign that to the log function so we’re exporting just the function and then when we utilize that in your application file we import it with cons log and utilize the required function and then we can simply invoke it by just calling log and passing in the message as the argument in conclusion the required function in nodejs is essential for modular programming allowing you to include and use JavaScript files and modules efficiently by following best practices for module loading and leveraging code quality tools you can ensure your node.js applications are robust maintainable and airfree what role does the require function play and managing dependencies and modularity within a node.js application the required function in node.js is crucial for managing dependencies and modularity by allowing you to load and use code from other files or modules within your application it enables you to break your application into smaller reusable components making your code more organized maintainable and scalable by importing only the needed functionality require helps keep your application structure clear and modular how can following best practices when using the require function contribute to the maintainability and reliability of a node.js code base following best practices when using the required function and node.js such as using the cons keyword for module Imports and keeping modules small and focus helps maintain a clear and consistent code structure this reduces the risk of Errors makes your code easier to understand and improves its reliability it also prevents accidental reassignment of modules and ensures that changes in one part of the code don’t unintentionally affect other parts contributing to a more maintainable and robust code base so let’s go over how nodejs processes modules node.js has a unique way of handling JavaScript code which differs significantly from how scripts are executed in a browser environment so let’s discuss module wrapping in node.js when node.js executes a module it does not run the code directly as written instead it wraps the module code inside a function this approach is not immediately apparent to the developer but it is fundamental to how nodejs operates so here’s what happens under the hood first is function wrapping each module is wrapped in a function before it is executed the function wrapper helps to isolate module from the global scope which means variables and functions defined in a module do not pollute the global scope so just to show an example of what this might look like we have in parenthesis can we Define function exports then require module and we’ll discuss this more in detail in this lesson just want to demonstrate a visual example of what this will look like directory name then the function block so your module code lives here let me rename this lives here so we to do say Con X assigned to below then we can log this out so when we Define these two statements so cons X assigned to a string and then logging it out node.js will implicitly wrap this module code inside a function so second is the module wrapper the function that wraps each module takes several important parameters which we specified here so the first is exports this is used to export module functions and variables the second is requir a function used to import the exports of another module the third is module which represents the current module next is the file name so two underscores and then file name so this refers to the file name of the module and then directory name so third is exporting from modules you can add properties to exports or module. exports to make them accessible to other modules like in our previous example when we did module. exports. log and assign this to the log function or we can do exports. log assign to log however replacing exports entirely won’t affect module. exports because exports is just a reference to module to exports using built-in modules node.js comes with a variety of built-in modules that provide rich functionalities like file system manipulation HTTP server creation and handling system pass these modules are essential tools for node.js developers and are thoroughly documented in the node.js API documentation so an example of using a built-in module here to do cons path and then we require the path let’s comment this out now we can get the path object so I’ll say path object sign two path dot parse then pass in file name and let’s log this out path object bring up our integrated terminal we’ll run this file and here it outputs this object showing my current file so in conclusion understanding how node.js executes module code and utilizes function wrapping provides a clearer picture of the runtime environment this process ensures that Global variables and functions from one module do not interfere with another fostering a more organized and secure coding environment furthermore node.js built-in modules are powerful tools that extend the functionality of node applications enabling developers to handle a wide range of system level tasks [Music] efficiently how does node.js module wrapping mechanism contribute to isolating module scope and preventing Global namespace pollution no. js’s module wrapping mechanism isolates each module scope by wrapping the module code in a function this prevents variables and functions defined in one module from leaking into the global scope reducing the risk of naming conflicts and ensuring that each module operates independently this mechanism helps maintain a clean and organized code base where Global namespace pollution is minimized making the application more secure and easier to manage what benefits do node.js built-in modules provide for handling system level tasks and application development no. js’s built-in modules provide powerful tools for handling system level task such as file manipulation network communication and managing paths these modules save developers Time by offering ready to use optimized functionality that integrate seamlessly with the nodejs runtime by using these built-in modules developers can efficiently manage system resources build robust applications and avoid the need to reinvent common functionalities leading to more secure maintainable and performant [Music] applications so let’s go over retrieving system information with the node.js OS module When developing applications that require system level data node.js provides a built-in module called OS which allows you to gather information about the underlying operating system so let’s cover using the OS module step one is to import the module so at the very start of file we’ll say cons we name it OS require and the name of it is OS for operating system so step two is to retrieve memory information so the OS module provides several methods to get system information such as os. tootal memory and os. free memory which Returns the total and free memory of the system respectively so we can do that const I’ll say total memory os. total M and then free memory os. free memory let’s log this out so I’ll say log I’ll use back tis say total memory and then hold on memory and I’ll do shift option and down arrow to copy this I’ll say free memory and let’s just copy and paste it here so open up the integrated terminal so that’s command J so let’s run this file with node and then the name of the file so here I get the expected output so this provides insights that are not typically accessible from client side JavaScript code which runs in the browser so in conclusion the OS module is a powerful tool in node.js for accessing operating system level information this can be particularly useful for applications that need to monitor or manage system resources using node.js developers can write server side code that interacts directly with the operating system offering capabilities beyond what is possible in a browser environment this makes nodejs a great choice for building more complex system sensitive backend [Music] applications how can the nodejs OS module be utilized to gather essential system information for applications that require insights into the operating systems resources the node.js OS module can be utilized to gather essential system information by providing methods to access details like total and free memory CPU architecture network interfaces and more this information is crucial for the applications that need to monitor or optimize system resources especially in server environments we’re understanding the underlying operating system can help in managing performance and resource allocation effectively the OS module allows developers to write scripts that interact directly with the operating system offering insights that go beyond typical client side capabilities what advantages does nodejs offer for building resource sensitive backend applications that need to interact with the operating system directly nodejs offers several advantages for building resource sensitive backend applications that need to interact with the OS directly it provides built-in modules like the OS module which allows access to system level information such as memory usage CPU details and network interfaces this direct interaction with the OS enables better monitoring management and optimization of system resources additionally node. js’s non-blocking I model makes it well suited for handling multiple tasks efficiently which is critical in resource sensitive [Music] environments so let’s go over understanding the node.js file system module node.js provides a powerful built-in module called FS for interacting with the file system this module is essential for reading from and writing to files on the server so first you would import the fs module so at the top of your script you can do const FS require and the name of it is FS for file system now let’s discuss the methods in the fs module so the fs module includes a variety of methods to handle file operations which comes in two primary forms the first being synchronous which is blocking and asynchronous which is non-blocking so for the first form which is the synchronous methods synchronous methods block the execution of further JavaScript until the file operation completes they are straightforward to use but can significantly slow down your application especially under heavy load so an example of this could be cons files and then fs. read directory sync so the pass in the current directory we can do console.log files so this will log all files in the current directory let’s run this and integrate a terminal so it’s node and the name of this file so here we see all the files in my current directory I’ll clear this out with command and J now the second form is asynchronous methods asynchronous methods on the other hand perform operations in the background and accept a callback function that runs once the operation completes this approach is non-blocking and allows node.js to handle other tasks while waiting for the file operations to complete so an example of reading directories asynchronously below I can do pass and also say async files just to give a different name so fs. rir directory first argument is the current directory and then it takes in a callback function so I’ll specify that to be an errow function so eror and then files So within it if there is an error and I will simply console log it so erir and then else console. log will say the result files so this will log the files once it’s read so let’s comment this up for now and let’s see the output when we do so asynchronously so once again we get the same result outputting all the files in my current directory so best practices for using FS methods the first best practice is avoiding synchronous methods in production while synchronous methods are easy to use and understand they should generally be avoided in production especially for iey operations a nodejs process runs on a single thread and using synchronous methods can block This Thread leading to Performance bottlenecks when handling multiple requests the second best practice is to prefer asynchronous methods asynchronous methods allow your node.js server to remain responsive by freeing up the main main thread to handle other requests while waiting for file operations to complete this approach is crucial for maintaining performance and applications that serve many clients simultaneously exploring the documentation for a complete list of available methods and additional details visit the official node.js documentation for the fs module this documentation provides comprehensive insights and examples for both synchronous and asynchronous methods in conclusion understanding and utilizing in the fs module and node.js is crucial for performing file operations effectively by preferring asynchronous methods you can ensure that your node.js applications remain efficient and responsive underload making full use of node. js’s non-blocking architecture what are the benefits and drawbacks of using synchronous versus asynchronous methods when performing file operations in node.js synchronous methods in node.js are easy to implement and use but they block the execution of further code until the operation completes which can lead to Performance issues especially under heavy load a synchronous methods perform operations in the background without blocking the main thread allowing the server to handle other tasks simultaneously this makes them more suitable for production environments ensuring better performance and responsiveness the draw call back is that they require handling callbacks or promises which can add complexity to the code why is it important to prioritize a synchronous methods for file system operations in production environments when using node.js it is important to prioritize asynchronous methods for file system operations and node.js production environments because they allow the server to remain responsive by freeing up the main threat to handle other task asynchronous operations prevent the application from being blocked by long running task which is crucial for maintaining high performance and efficiently serving multiple client requests simultaneously this helps ensure the application can scale and handle High loads without performance bottleneck so let’s go over understanding events and nodejs node.js is built around an event driven architecture primarily using an event Loop mechanism which makes it efficient for Io heavy operations so the core concept of events and node.js and event signify something that has occurred within the application for example when a server receives a request at a port it’s an event the nodejs runtime handles this event by generating a response so let’s go over using the event emitter class event emitter is a core class in node.js used for handling events within your application so here’s how you can use it step one would be importing the event emitter so first you need to import the event emitter from the events module so name this event emitter and I’ll use Pascal naming convention the require function and then events so step two is creating an instance so event emitter is a class and you must create an instance of this class to use it so this instance will manage the events for your application so we’ll name our object emitter use our new keyword to instantiate the new object so step three is registering listeners listeners are functions that are called when a specific event is emitted so use the on method to register a listener for an event so we’ll do emitter then the method on so we’ll name the event so this will be message log then we pass in a callback function so I’ll use the modern errow function syntax and we’ll just log out to the console and I’ll say listener call and save that so step four is emitting events the emit method is used to trigger an event when this method is called all register listeners for the event are invoked so we can do emitter do Emit and then we’re using the same name of the event for this event to have occurred so so it’s important to register listeners before emitting the event as they will not be triggered retroactively so let’s bring up the integrated terminal and we’ll run this file so here we see when we emitted this event it called the event handler which we pass in as the second argument here so let’s discuss event arguments events can also pass data to their listeners and you can send multiple parameters to The Listener function by passing them as additional arguments to emit so here we currently have an empty parameter list but we can specify this to be ar for example so let’s include that in our console log statement say R now when we emit it we could pass in an object so I can say the ID is one and the URL is Sten cod.com so now this second argument that we pass will be the argument that our event listener or event handler receives so let’s call this again and here we see we successfully passed data to our event listener so let’s discuss the Practical usage event emitter is widely used in node.js core modules like handling HTTP requests and web servers or reading files asynchronously developers can use this pattern to handle custom events in their applications enhancing the modularity and separation of concerns in conclusion the event emitter class is a fundamental part of node.js that helps manage events and listeners facilitating the event driven architecture that nodejs is known for proper use of this class can help you build robust and maintainable node.js applications by organizing operations around the handling of various system and custom [Music] events how does no js’s event driven architecture enhance the efficiency of handling IO operations node js’s event driven architecture enhances the efficiency of handling IO operations by using an event Loop

to manage multiple tasks without blocking the main thread when an i operation is initiated node.js can continue processing other tasks while waiting for the operation to complete this non-blocking approach allows node.js to handle many concurrent operations efficiently this non-blocking approach allows node.js to handle many concurrent operations efficiently making it ideal for applications that require high performance and scalability and auto intensive environments what role does the event emitter class play in managing events and listeners within node.js applications the event mitter class in node.js plays a central role in managing events and listeners it allows you to create and handle custom events within your application by using event emitter you can Define events register listeners that respond to those events and emit the events when certain conditions are met this helps organize your application around an event driven architecture enabling more modular maintainable and responsive code especially in applications with a synchronous operations so let’s go over handling data with events and node.js when working with a node.js event and M class it’s common to send additional data about an event this can help listeners perform their tasks more effectively by providing them with the necessary context so let’s cover emitting events with data when triggering an event you can pass data as arguments to the emit method this data can be accessed by the event listeners so first we will cover passing multiple arguments while you can pass multiple arguments separately it is generally more manageable to encapsulate them in an object as we did in the previous lesson so I’m going make a copy of this so I’ll sh option and down arrow so in the previous example we passed all the data and capsulate within an object but we also can just pass them as an argument so passing in the ID value and the URL but this is less manageable as it has less context so we prefer to use an object because the name of the property indicates what this value represents so it’s not just a magic number right it has more context so by passing an object you can include multiple pieces of data under a single event argument which makes handling this data in listeners simpler and more organized let’s clear this out so now let’s cover registering listeners to handle data listeners can be set up to receive event data here’s how to define listeners to handle the data pass to them so using a function to listen for events you can Define listeners using either traditional function syntax or es6 Arrow functions both methods allow you to access the event data passed from the emit call so in the previous lesson we use es6 Arrow functions to copy this we could also used traditional function syntax so remove that arrow and this will work as well so in both cases the argument right so this parameter that we specified also commonly called event args or simply e represents the data object pass from the imit method so I remove this and we’ll stick with the more modern syntax so let’s go over a practical example which is a custom logging event so consider a scenario when you want to log custom messages so you can set up a specific event for logging messages and emit data related to those messages so let’s do we can comment this out since you don’t need that right now emitter Doon and we’ll name this event to be logging the pass in an eror function this accepts parameter of data and we’ll log out I’ll say receive message and we’ll do comma data. message so now we can emit a logging event with the message data so emitter emit so the name of this event which is logging we’ll pass in that data object which has a proper a message and I’ll just say hello so I’ll bring up the integrated terminal command J then the name of this file we run it with node and I get the expected console output when we call it emit for this event to occur so here the logging event is configured to pass an object containing a message and The Listener logs this message when the event is emitted so in conclusion using event emitter and nodejs to handle events with additional data is a powerful pattern for developing modular and responsive applications by encapsulating data in an object and passing it through events your application can maintain clear and manageable communication between different parts of your system this approach not only keeps your code organized but also enhances its flexibility and scalability how does passing data through events improve communication and modularity within a node.js application passing data through events in a nodejs application improves communication and modularity by allowing different parts of the application to interact efficiently it’s able to do so without direct dependencies it enables event listeners to receive relevant data when an event occurs promoting a clear separation of concerns this modular approach makes the code more organized flexible and easier to maintain as components can respond to events handle data independently what are the benefits of encapsulating event data in an object when using the node.js event M Class encapsulating event data in an object when using the node.js event emitter class provides several benefits it allows you to pass multiple related pieces of data as a single argument making the event handling code more organized and easier to manage this approach also enhances readability and scalability as the object structure can easily be extended to include additional data without altering the function signatures or logic it simplifies the communication between different parts of the application ensuring a cleaner and more modular [Music] design so let’s go over integrating event emitter into custom classes in Rob applications it’s uncommon to use event emitter directly instead you typically extend event em emitter in a custom class to encapsulate related functionalities along with event handling capabilities extending event emitter allows you to build self-contained components that can generate events and handle their own functionalities this is particularly useful for creating modules that need to perform actions and then notify other parts of your application that those actions have completed so we’ll go through the process of creating a logger class that extends event emitter to handle logging operations and emit events so Step One is defining the loger class we create a new directory and I’ll name this 15 custom class event emitter so in this directory I will create logo. JS let’s import event emitter this will be the base class that is from events so now we’ll Define our custom class which is lo ER and we want to extend the functionality CU logger is in an event emitter extends event emitter so it inherits all its functionality so now let’s define our log method the log takes in message as its parameter variable I a comment here and I’ll say logic to log and HTTP request or any message so do console.log of the message add another comment so I’ll say emitting an event when the log method is called so I’ll say this so This current object I’ll call emit since logger is an event emitter We inherited this emit method for to call or invoke an event this will call the event logged event and we’ll pass in the ID and the URL just say stepen craft.com just for example now once again this class is only available within this file or within this module so we need to explicitly export it so I’ll say module to exports on to logger so we’re exporting this class create a new file here and I’ll name it app.js and we want to utilize this logger class we just defined let’s import it so logger require it’s name logger I’ll instantiate it right so we’re creting a new instance of that log class that we defined a comment here and I’ll say registering a listener for the message log event right so we need to Define this event and listener before we call it right so we named it message logged so I’ll say logger do on message log for the second argument takes a callback function so we use the modern P6 errow function syntax log to the console and we will log out listener received an argument and now let’s actually call that log function so add a comment here I say calling the log method which will trigger the message logged event right so we’re calling this method that we Define here so I’ll say logger.log of not to say hello world let’s bring up the integrated terminal then I’ll navigate to this directory that I created with 15 custom and now I’ll run node app.js so here we see it logged out we go to the implementation of this it logged out the message which was hell world and then it logged out what we had in this event listener so listener received and then the data that we passed to it so let’s go over the benefits of this approach the first benefit is encapsulation the logger class encapsulates both the logging functionality and the event handling making it modular and easier to manage the second benefit is reusability by abstracting the event emitter Behavior into a class you can reuse and extend this class wherever needed without rewriting the event handling Logic the third benefit is maintainability having a dedicated class for logging and event emission helps maintain and modify logging Behavior independently from the rest of your application let’s go over a common mistake so a common mistake when starting with event emitter is to create multiple instances of the emitter when only one is needed or to bind listeners to different instances than the emitter that emits the event this is why encapsulating the event emitter within a class as shown ensures that the event listeners are correctly associated with the specific instances of the class that emits the events in conclusion by extending event emitter and custom classes like logger nodejs applications can handle complex functionalities while efficiently communicating events across different modules this pattern enhances the modular architecture of the application promoting clean and manageable code that aderes to Modern software design [Music] principles what are the advantages of integrating the event emitter class into custom classes when building modular components in node.js integrating the event emitter class into custom classes and node.js allows you to build modular components that can handle specific task and emit events related to those tasks this approach encapsulates functionality and event management within a single class making the code more organized reusable and easier to maintain it ensures that event handling is tightly coupled with the relevant functionality improving the overall architecture and communication between different parts of the application how does extending event emitter and custom classes enhance the reusability and maintainability of node.js applications extending event emitter in custom classes enhances reusability and maintainability by encapsulating both functionality and event management into a single self-contained mod modol this allows the class to be easily reused across different parts of an application or in other projects without duplicating code it also simplifies maintenance because the logic for emitting and handling events is centralized making it easier to update or modify without affecting the rest of the [Music] application so let’s cover creating a web server with no. JS node.js provides the HTTP module a powerful tool for developing networking applic such as web servers that listen for HTTP requests on a specified Port let’s cover the basic web server setup so the first step is to import the HTTP module the HTTP module includes the functionality necessary to create server instances so we can do cons HTTP require HTTP so the second step is to create a server use the create server method to create a new server the server can handle http requests and responses we do cont server assign to http create server step three is listening to events the server object created by HTTP create server is an instance of event emitter this means you can listen to events like connection for lower level Network events you can do server.on the event of connection and we’ll pass in our call back so the parameter will be socket and we’re using our modern es6 errow function syntax ended with the semar colon and for now we’ll just log to the console new connection and save that so step four is starting the server we’ll have the server listed on a port such as 3001 to handle incoming requests so we could do server. listen at 3001 and we’ll log out to the console listening on Port 3001 so now let’s run this and integrated a terminal so here we see it’s listing on P 3001 if we navigate to our web browser so now if I navigate to Local Host 3001 let’s resize this back in vs code we see it says new connection which is this console log statement here close this out and contrl C to stop this program so handling HTTP requests more efficiently while the above method works for simple demonstrations handling HTTP requests based on different routes can be done more effectively so step five would be refining the server to handle requests instead of listening to the connection event you can directly handle HTTP requests by providing a call back to create server that deals with request and responses so here where we called create server we pass in the call back function so the request and the response using our Arrow function syntax so if the request URL is at the index right so just a for slash we can do response. right hello world and who will end the response otherwise we can say if request URL is at API courses we can say response. right json. stringify we’ll just say an array of one two and three and response. end so let’s run this again up Arrow run so once again it’s listing on that Port you can navigate to it I’ll say Local Host 3001 and here we see hello world as specified and we did response. right now if we navigate to this path add this to the end and here we see this array that we specified here so this setup directly responds to http get requests at the root with the for slash as well as at API SL courses which sends a Json response in this case an array let’s close this with contr C close it out so using Express for complex applications for more complex web applications managing routes with the native HTTP module becomes cumbersome this is where Express a web application framework built on top of the HTTP module comes in handy so let’s discuss the advantages of Express the first being simplification of routing Express provides a much cleaner and organized way to handle different HTTP routes with minimal effort second Advantage is middleware support Express allows you to use middleware to respond to http requests handle errors and process data and third is enhanced server capabilities while Express uses the underlying HTTP module it simplifies many tasks and adds powerful new features and to discuss what an example of this might look like you need to utilize the express mpm module and create a package.json file after you import Express you can create an instance of of it by calling Express then you can Define the get request for both the root path as well as the API for/ courses path so in conclusion starting with node js’s HTTP module is great for learning the basics of network communications in JavaScript however for building more sophisticated applications such as a framework like Express can greatly simplify your code and enhance your server’s functionality making it easier to maintain and expand [Music] what are the benefits of using the node.js HTTP module to create a basic web server and when might you consider using a framework like Express instead using the node.js HTTP module to create a basic web server is beneficial for learning the fundamentals of network communication and handling HTTP requests directly it offers full control over the server’s Behavior with minimal overhead how however for more complex applications a framework like Express is preferable because it simplifies routing supports middleware and adds powerful features making the development process faster more organized and easier to maintain as the application grows how does the event driven nature of node.js influence the design and functionality of a web server created with the HTTP module the event nature of node.js influences the design and functionality of a web server by allowing it to handle multiple requests concurrently without blocking the main thread this non-blocking iio model ensures that the server can efficiently manage incoming connections and process requests as events responding to them asynchronously this design is particularly well suited for high performance applications where the server needs to remain responsive and scalable even under heavy load so let’s summarize what we covered for the node module system first we covered an introduction to nodejs this part of the course provides a foundational understanding of what node.js is and the benefits of using it then we cover node.js architecture we explain the internal architecture of node.js including its non-blocking event driven nature that allows for high performance across rward applications we did a deep dive into nodejs functionalities where we covered how node works so we learn more about the underlying Mech mechanisms that power node.js such as the event Loop and asynchronous programming we covered an introduction to the node module system where we discussed the modular structure of node.js applications emphasizing how modularity is achieved and managed we covered working with node.js modules which includes Global objects so this covers buil-in Global objects and node.js which are accessible across all modules covered modules and focus on the importance of modules and node.js for organizing and maintaining code we went through creat and loading modules we covered practical guidance on how to create your own modules and how to import existing ones module wrapper function this section covered how node.js wraps module code within a function to maintain module scope and privacy then we went through and covered specific nodejs modules starting with the path module so this introduces utilities for handling and transforming file paths the OS module which provides information about the computer’s operating system where the nodejs application is running the file system module so this demonstrated how to work with the file system for reading from and writing to files and the events module so we discussed the event emitter class and how to handle custom events and applications we went through more advanced Topics by covering event arguments which detailed how to pass and handle data with events using the event emitter then we extended the event emitter where we learn how we can enhance and customize the event emitter for more complex event handling scenarios lastly we covered the HTP module so this outlined how to to use node.js to create web servers and handle HTTP requests effectively in conclusion this section covered the fundamentals of how to use nodejs and its module system for building scalable and efficient applications by understanding and utilizing the core modules and Architectural principles of node.js developers can create robust backend services and applications suited for a variety of world world tasks [Music] in node.js development managing third-party libraries and modules is facilitated by package managers the two primary package managers used in the nodejs ecosystem are mpm which stands for node package manager and yarn so first let’s go over understanding mpm mpm is not only a package manager but also a registry that hosts a vast collection of free open source libraries these libraries can be easily integrated into your nodejs projects to add new functionalities let’s go over mpm Basics the registry visit npmjs.com to explore a wide range of packages available for various functionalities these packages are open source and free to use installation mpm comes bundled with node.js so when you install node.js you automatically get mpm installed on your system to check the version of mpm that you have installed in your system from the command line you can run mpmv So currently I have 10.8.2 installed on my system now to update mpm and to ensure that you have the latest features and security patches you can update mpm to a specific version globally using the following command so here I’m using a Mac so I’ll use the command sudu mpm install then the flag DG mpm at latest or enter my password this will update it so I use the latest version now we use mpm to install open source packages to add a package to your project you would use the command mpm install and then the name of the package so let’s discuss Global versus local installation by default mpm installs packages locally within your project however some tools need to be available globally to be run from anywhere on your system so you would do that with mpm install then use the flag – G and then the package name introduction to yarn yarn is another popular package manager that could be used as an alternative to mpm it was created by Facebook and is known for its speed reliability and improved Network performance installing yarn unlike mpm yarn is not bundled with no JS and must be installed separately you can install yarn globally using mpm so the command to install it is mpm install DG and then the package name which is yarn using yarn let’s cover how you can add a package with yarn similar to mpm you can add packages to your project with the command yarn add and then the name of the package why use yarn yarn caches every package it downloads so it never needs to download the same package again it also paralyzes operations to maximize resource utilization and thus install packages faster publishing your own package if you’ve developed a functionality that could benefit others you can publish your own packages to mpm making it available to the global node.js community so first you would prepare your package so ensure that your package is well documented has a clear readme file and includes all necessary metadata in your package.json file step two is publishing so you would run the commands mpm login after you loging with your credentials then you would run the command mpm publish in conclusion mpm and yarn are essential tools for any node.js developer they simplify the process of integrating thirdparty libraries into your projects manage independent effectively and helps you contribute back to the community by publishing your own packages whether you choose npm or yarn depends on your specific needs and preferences as both provide robust features to streamline development workflows what are the key differences between mpm and yarn in terms of speed reliability and package management features the key differences between mpm and yarn are speed reliability and package management so when covering speed yarn generally installs packages faster than mpm because it paralyzes operations and caches packages locally reducing the need for repeated downloads for reliability yarn ensures consistency by using a lock file which is named yarn. loock to keep track of exact package versions which helps avoid version mismatches so when considering package management yarn offers better off find support and more efficient dependency resolution while mpm is more integrated with the node.js ecosystem and its package registry how do package managers like mpm and yarn contribute to efficient dependency management and no. JS projects package managers like mpm and yarn contribute to efficient dependency management and node.js projects by automating the process of installing updating in organizing thirdparty libraries they manage versioning to ensure compatibility handle dependency trees to prevent conflicts and streamline workflows through commands for adding removing and updating packages both tools also maintain lock files to ensure consistent environments across different development setups making it easier to collaborate and maintain project stability so let’s cover setting up a node.js project with mpm when starting a new nodejs project one of the first steps is to set up a package.json file this file contains metadata about your project and manages the Project’s dependencies so let’s go over creating a new project directory I’ll open up the integrated terminal let’s expand this and we’ll create a new directory so mkd and I’ll name the directory mpm DDO we’ll change into that new directory now we will initialize our package Json file so before adding any node packages to your project you need to create a package.json file this file will track your project dependencies and store other important project information we’ll create this file by using the command mpm andit so mpm initialize so this command will prompt you to enter several pieces of information such as the Project’s name the version description the entry point such as an index.js file the test command repository keywords author and license so these details help Define and document your project so I have to say enter so the project name will be mpm demo the version is 1.0 the description I’ll say lesson on node package manager entrypoint index.js file test Comm I to say enter author I’ll say Steven Garcia license and I’ll say yes so now if we list that we see it has created our package.json file so let’s view this by expand here in mpm demo this is the package.json file that it created for us now let’s cover automating package.json creation if you prefer to skip the manual input and use default values for your package.json you can use the D- yes flag so previously we just did mpm and nit but instead you can do mpm andit D- yes so this command automatically fills in default values for all the fields in the package.json file speeding up the setup process so let’s cover the importance of the package.json file the first is Project metadata the package of Json file holds key information about your project which can be useful for package management and during deployment so let’s discuss dependency management it lists all the packages your project depends on allowing mpm to automatically install and manage these packages for you script shortcuts you can Define scripts and package.json that you can run with npm this is useful for tasks like starting the server running tests or custom build processes best practices one best practice is regular updates keep your package.json file updated as you add or remove dependencies update scripts or change project metadata Version Control include package.json in your version control system such as get Version Control to ensure that team members and deployment environments use the correct project settings and dependencies in conclusion the package.json file is a fundamental component of any nodejs project serving as the blueprint for managing the project settings and dependencies by starting your project with the creation of this file you ensure that all dependencies are correctly tracked and that your project metadata is well documented from the beginning this initial setup is crucial for maintaining a health manageable codebase as your project grows why is the package Json file crucial for managing dependencies and project metadata in a node.js project the package.json file is crucial in a node.js project because it serves as the central hub for managing project dependencies scripts and metadata it tracks all the libraries your project relies on ensuring consistent installation across different environments additionally it stores important project information such as the version author and Licensing details and provide scripts for common tasks making the project easier to manage share and deploy this file is essential for maintaining an organized and efficient code base how ises initializing a node.js project with mpm and knit contribute to better organization and maintainability of the Project’s codebase initializing a no JS project with mpm a nit contributes to better organization and maintainability by creating a package.json file that centralizes project metadata and dependency management this file keeps track of all libraries and modules the project depends on ensuring consistent setups across different environments it also allows you to Define scripts for common task making your workflow more efficient and the project easier to manage as it grows this structured approach prompts a well organized and maintainable code base from the start adding a third-party library to your node.js application integrating thirdparty libraries into your node.js project can enhance functionality without the need to write additional code libraries such as underscore provide a range of utilities for common programming task so Step One is choosing a library so begin by choosing using a library that suits your needs for instance underscore is a popular JavaScript library that offers helpful functional programming utilities you can search for underscore or other libraries on npmjs.com which also provides installation instructions and documentation for each package so step two is installing the library to add a library like underscore to your project use the mpm install command this command downloads the library from the mpm registry and adds it to your project so let’s open up the integrated terminal with command J we can run mpm install underscore alternatively you can use a shortcut mpm icore when you install a package using mpm two important things happen the first is an update to your package.json file so here when we install underscore it is added within the dependencies object this entry ensures that any one else working with your project repository can install the same dependencies and the second is Library storage the library files are downloaded and stored in the node modules directory within your project so here we see has created a node modules directory which contains our dependencies so step three is using the library in your application so after installation you can require and use the library in your application files so let’s create a new file in our mpm demo directory and name it index.js as that is the entry point of our application let’s close the sidebar now we can utilize the underscore Library so I’ll say require and underscore so by convention we use the underscore when using this library now we can say cons is even underscore and then the method sum so I’ll pass in an array 1 2 3 4 and five and for the second argument I’ll pass in a call back so a number if a number is divisible by two then we’ll log out let me make let me rename this to be is even then I’ll log out is even so this method sum checks if at least one of the elements is even let’s run this so I’ll say node index.js and here I see the output of true so in conclusion adding thirdparty libraries like underscore to your node.js projects streamlines development by allowing you to utilize pre-built functionalities this practice not only saves time but also enhances the capabilities of your application always ensure to use while maintained and trusted libraries manage your dependencies through package.json keep your projects organized and maintainable what are the key considerations When selecting and integrating third party libraries into a node.js project When selecting and integrating thirdparty libraries into a node.js project key considerations include ensuring the library is wellmaintained and widely used which indicates reliability and Community Support check for compatibility with your Project’s node.js version and evaluate the library’s documentation and features to ensure it meets your specific needs also consider the potential impact on your Project’s performance and security properly manage these dependencies in your package.json file to maintain an organized and maintainable codebase how does managing dependencies through mpm enhance the organization and maintainability of a node.js application managing dependencies through mpm enhances the organization and maintainability of a node.js application by automatically tracking all required libraries in the package.json file this ensures that all dependencies are documented and can be easily installed or updated by other developers or in different environments mpm also handles versioning preventing conflicts and ensuring consistent environments across different setups this structured approach helps keep the project organized and simplifies dependency management making the application easier to maintain over time using thirdparty libraries like underscore can significantly streamline complex operations and no JS applications so in our index.js file we imported our underscore Library so it’s common to use the underscore symbol as the variable name for this particular Library so the require function follows these steps to locate the under underscore module it first checks if underscore is a core node.js module failing that it looks for underscore as a relative or absolute path in the project lastly it searches within the node modules directory so the underscore Library provides a wide range of utility functions that are highly useful for working with collections arrays and objects for example to check if an array contains a specific item you can use the contains function so here I can comment this out so command and Port slash so I can say cons does contain uncore do contains so for the first argument I’ll pass an array containing one two and three and for the second argument I’ll pass the value two and let’s log out the result does contain so we’ll do up arrow and run and here we see the value true let’s say if I change this to be the value four then we would see that it does not contain the value of four to better understand all available functions and their uses in the underscore Library visit the documentation so when viewing this particular library on npmjs here when it says homepage you can view the documentation for the library that you installed so this can provide insights into additional methods and their potential applications in conclusion using libraries like underscore and nodejs projects helps to reduce the amount of code you need to to write while increasing functionality and readability it is essential for developers to familiarize themselves with importing modules and understanding the path resolution mechanisms of node.js to effectively manage and utilize various libraries this practice ensures your applications are both efficient and [Music] scalable what are the benefits of using thirdparty libraries like underscore and no. JS projects and how can they enhance the efficiency of your Cod cod using third party libraries like underscore and node.js projects provides ready-made utility functions that simplify complex task reducing the amount of code you need to write this enhances code efficiency readability and maintainability by leveraging well tested functions from libraries you can focus more on building unique features rather than Reinventing common functionalities leading to faster development and more robust applications how does understanding no. js’s module resolution process help and effectively managing and integrating external libraries into a project understanding no. js’s module resolution process helps in effectively managing and integrating external libraries ensuring that you know how node.js locates and loads modules this knowledge allows you to correctly structure your project avoid conflicts and troubleshoot issues related to module pass it also ensures that the right version of dependencies are used which is crucial for maintaining a stable and predictable development environment this leads to smoother integration of external libraries and more reliable application [Music] Behavior When developing applications with no JS managing external libraries and dependencies is commonly handled using mpm which stands for node package manager so here’s how you can install a package like axios which is widely used for making HTTP requests to apis so we’ll open up our integrated terminal let’s clear this out we’ll use mpm and then I for install and then the name of the package which is axios so this command fetches the package from the mpm registry and installs it into your project you can view our package.json file and here we see axos is now included in the dependencies object if we view our no modules we also see the axios has been installed here so you’ll notice that it contains not only axios but also several other directories these are dependencies that axios requires to function properly so we can close this directory and navigate back to our index.js file so let’s discuss dependency management so when considering the file structure in the past mpm used a nested structure where each package would have its own known modules directory containing its dependencies this often led to duplication and a deeply nested directory structure which would cause path L issues especially on windows so for the current approach now mpm installs all dependencies in a flat structure in the root node modules directory of your project this change helps avoid redundancy and the complications of deeply nested dependencies handling version conflicts if different packages require different versions of the same dependency mpm will Nest the conflicting version locally within the requiring packages directory to avoid version clashes at the root level so let’s discuss the benefits of the current approach the first being simplification the flat structure simplifies dependency management by reducing redundancy and the potential for version conflicts across your project the second benefit is efficiency it minimizes dis space usage and improves installation speed since mpm no longer needs to install multiple instances of the same package across different locations the third benefit is compatibility it reduces issues related to file pad limits on certain operating systems which is particularly beneficial for Windows users so let’s go over a practical example with the axos library so now that we installed it we can start using it in our nodejs application to make HTTP requests so here’s a simple example to include axios in our project so we can do const axios use our require function the name of it is axios let we close the sidebar so we can do a.get for making a HTTP get request and we’ll make a request to an open source URL so https Json placeholder do typec code.com SL too SL1 then we’ll do then cuz it returns a promise which we will cover in the next section so response then we want to log this out response.data we’ll also include or chain catch for handling if any err occurs so we will log out the air console. a air. message and we’ll end that with the semicolon also we need to add another parentheses here to get rid of those errors so let’s run this with node index.js and here we see the data that we retrieved from this backend endpoint so this object contains a user ID an ID a title and a property of whether it is completed or not for this to-do item so in conclusion installing and managing node packages with mpm is a straightforward process that enhances the functionality of your applications understanding how mpm handles dependencies allows you to better organize and optimize your projects by using tools like axios developers can easily make HTTP requests in their applications making the development process more [Music] efficient what are the advantages of mpm’s flat dependency structure in modern node.js projects particularly in terms of efficiency and compatibility mpm’s flat dependency structure improves efficiency by reducing redundancy as it avoids multiple copies of the same package being installed in different locations this structure also minimizes disc space usage and speeds up installation times in terms of compatibility it reduces the likelihood of Path Lane issues especially on Windows and simplifies dependency management by making the directory structure less complex and easier to navigate this approach leads to a more streamlined and manageable project setup how does understanding mpm’s dependency management process benefit developers when integrating external packages like axios into a node.js application understanding mpm’s dependency management process benefits developers by ensuring that they can effectively handle and resolve potential conflicts between different versions of packages required by their node.js application it helps maintain a clean and organized project structure preventing issues like redundant installations or version mismatches this knowledge is crucial when integrating external packages like axios as it ensures smooth installation compatibility and Optimal Performance of the application leading to a more reliable and maintainable code [Music] base so first let’s discuss the role of know mod modules so its role is the storage of dependencies so let’s go over managing node modules and nodejs projects when working with node.js the node modules directory can become quite large because it contains all the packages you’ve installed using mpm along with their dependencies here’s how to efficiently handle this directory especially in collaborative environments so node modules hold all the packages that your application needs to run which are installed based on the list of dependencies found in your package.json file so why exclude known modules from Version Control so when working with applications we use G Version Control in order to manage our project as well as collaborate with other developers now we want to exclude the no modules directory when working with virion control the first reason being is size considerations this folder can become quite large and grow to hundreds of megabytes or more due to the nested dependencies typical in node.js projects including it in vers control would significantly increase the size of your repository and slow down operations like cloning and pulling changes the second reason is reproducibility so every dependency and its exact version is already specified in our package.json file so here if I view that so this means that node modules can be recreated on any Machine by running mpm install so there’s no need to include it in Version Control so let’s discuss these steps to exclude node modules so we want to exclude the known modules when using get Version Control and this is essential for keeping our repository clean and lightweight so I open up the integrated terminal with command J so in this course I won’t cover get Version Control in depth I’ll just provide a quick explanation of how you can exclude no modules so we can initialize get in our current project so I’ll say get a nit so this initializes a new get repository so we can now use Version Control to manage our project we can do get status and we can all the files in our project now we want to create a dog ignore file so this file tells G which files or directories to ignore in your projects so I’ll create that here I’ll say touch. get ignore so let me close this with command J and we’ll view this file we just created so this is a hidden file and that’s why I prefix it with a period so we want to add the following line and this will specify that the node modules directory should not be tracked by git so I’ll say say node modules and then slash indicating the directory so we save this so now when we run get status to see what files are in our project here it doesn’t include the node modules directory so we can now add and commit our changes so we will add our changes to the staging area so we’ll say get ad and then period meaning all files let’s do get status again and here we see our project files are now staged and ready to be committed so we can do get commit Das message and I’ll name it initial commit so now these files are being tracked and I can collaborate with other developers who also have access to this project and are using get Version Control so let’s discuss restoring no modules if you clone the project or need to restore dependencies simply run mpm install in your command line so this command looks at your package.json file and installs all the necessary packages from the mpm registry so in conclusion excluding known modules from Version Control is a best practice in nodejs development it keeps your project repository manageable speeds up operations like cloning and ensures that all developers are working with the same dependencies as defined in package.json so this approach Fosters a clean more efficient development environment [Music] why is it important to exclude the node modules directory from Version Control and how does it benefit the management of a node.js project it is important to exclude the node modules directory from Version Control because it significantly reduces the size of the repository making operations like cloning and pulling changes faster the node modules can can be recreated at any time by running mpm install which installs all necessary dependencies based on the package.json file this approach ensures that everyone on the project works with these same dependencies while keeping the repository clean and efficient to manage what are the best practices for managing dependencies and restoring them in a node.js project particularly in a collaborative environment best practices for managing dependencies in a node.js project include using a package.json file to track all dependencies and their versions this ensures consistency across different environments in collaborative environments it’s crucial to exclude the known modules directory from Virg control to keep the repository lightweight and avoid unnecessary duplication to restore dependencies use the mpm install command which installs everything listed in package.json ensuring all team members work with the same setup reducing the risk of conflicts or errors so let’s cover understanding semantic versioning and nodejs semantic versioning is a standard for versioning software which is widely adopted in the development Community including nodejs packages it helps developers understand the potential impact of updating a package so let’s discuss the components of semantic versioning a typical version number format includes three components the first being the major version the minor version and a patch version so for the major version this indicates significant changes that make API changes which are not backwards compatible upgrading to a different major version could break existing functionalities so for the minor version this adds new features in a backwards compatible manner it does not break or change existing functionality but adds to it and for the patch number this includes bug fixes and minor changes that do not affect the software’s function ality or API so it’s also backwards compatible so for example for the axios package that we installed one is the major version seven is the minor version and five is the patch version let’s discuss the carrot and the Tilda inversion name so here we see the semantic version number is prefix with a carrot so when you see a carrot in front of a version number in package.json it means mpm can install updates that do not modify the leftmost nonzero digit in the semantic versioning string so here for this particular example so here when considering axios since it is prefixed with a carrot it can install any version as long as the major version does not update even if the minor or patch version is higher than specified in our package.json file now you may also see a Tilda symbol so a Tilda allows updates that only change the most right-and digit that is not zero in the semantic versioning string assuming that the most right hand digit is the patch version so for example if the version was 1.3.6 mpm can update to 1.3x where X is any patch number greater than six this means you get bug fixes and minor changes that are unlikely to break your project so we can discuss installing packages with mpm so when someone CLS a repository and runs mpm install mpm installs the dependencies based on the rule set in the package.json file using the Carro symbol or tiled operator this allows for a controlled upgrade path that balances stability with getting timely patches and features specifying exact versions in some cases especially when ensuring absolute consistency across environments or dealing with very sensitive dependencies you might want to pin dependencies to an exact version to do this you can specify the version without any prefix this configuration guarantees that no version larger than the semantic version number specified will be installed avoiding any issues due to minor updates or patches in conclusion understanding how semantic versioning works with mpm helps manage dependencies more effectively ensuring that applications remain stable while still receiving necessary updates and Bug fixes it allows developers to control the risk associated with automatically updating packages and ensures that all team members and production environments run the same versions of each package how does semantic versioning help developers manage dependencies and ensure stability and node.js projects semantic versioning helps developers manage dependencies by clearly indicating the impact of updates through version numbers it uses three components a major minor and Patch to Signal the type of changes made major versions indicate breaking changes minor versions add new features without breaking existing functionality and Patch versions include Backward Compatible bug fixes this system ensures that developers can update packages safely maintaining stability while still receiving important updates and fixes reducing the risk of unexpected issues in your project what are the implications of using the carrot symbol or toota operator inversing when managing package updates and no. Js using the carrot inversing allows updates to minor and Patch versions while keeping the major version stable ensuring backwards compatibility the Tilda operator restricts updates to only patch versions keeping both major and minor versions fix these operators help manage package updates by allowing controlled upgrades the carot symbol offers more flexibility by permitting minor updates while the Tilda operator provides stricter control reducing the risk of breaking changes this helps maintain stability while still applying necessary updates so let’s discuss checking installed versions of a nodejs package so when managing a nodejs project it’s essential to keep track of the versions of packages installed to ensure compatibility and stability so here’s how you can determine the versions of the packages you have installed so viewing installed versions the first thing you can do is manual checking sometimes you may want to manually check the version of a specific package installed in your project this could be done by looking at the package.json file within each package’s directory and know modules so if I were to expand know modules and View axios and then package.json I see that the exact version installed is 1.7.5 so if I close this now we get back to our package at Json so the second way that you can check your installed version is using mpm commands so this is a more efficient way to view all installed packages and their versions by using the mpm list command so this displays the tree of packages installed in your project running this command in your project directory will show you a tree structure of all packages including their dependent packages so let’s open up the integrated terminal and we’ll run mpm list so this is a small project so we see our two mpm packages that we have in installed however this output can be extensive because it includes all nested dependencies in the case when we’re considering a large production application so the third way that we can check the version that we have installed is by running mpm list and then depth set to zero so if you’re only interested in the top level packages so those directly specified in your projects package at Json you can simplify the output using the depth set to zero option so this command restricts the output to the first level of the dependency tree showing only the packages that you have directly installed in your project so why this matters the first reason why this matters is compatibility knowing the exact versions of the packages you have installed helps manage compatibility between different parts of your application and its dependencies the second reason is debugging when troubleshooting issues in your application knowing the exact versions can help determine if a specific version of a package might be causing the problem the third reason is updates and upgrades regularly checking installed package versions can help you decide when to upgrade to a newer version and take advantage of new features or important bug fixes in conclusion effectively managing package versions in a node.js project is crucial for maintaining the stability and reliability of your applications using tools like mpm list helps streamline this process are providing a clear overview of what is installed thus enabling better version control and dependency management by routinely checking and upgrading your dependencies you can ensure your application remains secure efficient and up to [Music] date why is it important to regularly check the versions of installed node.js packages in a project regularly checking the versions of installed node.js packages is important to ensure compatibility and stability in your project it helps you identify potential issues caused by outdated or conflicting dependencies and allows you to take advantage of security patches bug fixes and new features keeping track of package versions also AIDS in debugging as knowing the exact versions can help pinpoint problems related to specific updates or changes in the package ecosystem this practice contributes to maintaining a reliable and secure application how can using npm commands help streamline the process of managing and verifying package versions in a node.js project using mpm commands streamlines managing and verifying package versions by providing quick and detailed insights into the installed dependencies commands like mpm list display all installed packages and their versions while options like the depth set to zero focus on top level dependencies making it easier to track and manage them this approach helps ensure your project remains stable and up toate by allowing you to easily monitor an update packages as needed all from the command line when working with mpm packages it is often necessary to understand their dependencies versions and other metadata to ensure they fit well within your project so let’s go over viewing package metadata on npmjs.com so here on the mpm official website search for a package you’re interested in such as axios so in this input field I’ll look up axios we will click on the official package so on the package page you will see comprehensive details including the latest version the licensing the GitHub repository the number of weekly downloads and the package dependencies so using mpm commands to view package information for a more direct and detailed exploration of a package metadata you can use mpm commands so open up the integrated terminal with command and J move this up so to see a summary of metadata for a package directly in your command line you can use the mpm view command so I’ll do mpm View and then the name of the package so this case it’s axios so this command let’s move this up so this command outputs information such as the latest version the description of the package the main entry point the repository keywords the author the license now let’s go over viewing dependencies if you’re specifically interested in what dependencies a package has you can directly view that information by typing in mpm view the name of the package so axios and then dependencies so this will list dependencies required by axios showing you what packages it relies on to function so checking available versions to view all versions of a package that have been published to mpm you can use mpm view the name of the package and then versions so this is particularly useful if you need to upgrade or downgrade to a specific version it lists every version available helping you make informed decisions based on the features or fixes included in each so a practical usage of package information the the first practical usage is for making upgrades knowing the version and dependencies can help you decide whether to upgrade a package you can assess the changes between versions and determine if the upgrade addresses any issues you face or offers new features you need compatibility checks viewing dependencies ensures that the package is compatible with other components of your application especially if there are specific versions of dependencies that your application requires debugging and issue resolution detailed metadata can assist in debugging issues related to package configurations or interactions between multiple packages in conclusion understanding how to retrieve and utilize metadata about mpm packages is essential for Effective package Management in no. JS projects whether it’s through browsing npmjs.com for a high level overview or diving deep with mpm view commands for specific details these tools provide critical insights that help maintain the health and functionality of your application [Music] why is it important to regularly check the dependencies and versions of mpm packages in a nodejs project and how can this practice impact the stability and compatibility of the application regularly checking the dependencies and versions of mpm packages in a node.js project is crucial for maintaining stability and compatibility it ensures that all packages work well together preventing conflict that could arise from incompatible versions this practice also helps identify when updates or security patches are needed reducing the risk of bugs or vulnerabilities by staying on top of package versions developers can keep the application reliable and ensure it runs smoothly across different [Music] environments When developing applications you might occasionally need to install a version of a package that isn’t the latest due to compatibility issues specific features or other dependen in your project this can be accomplished easily using mpm commands specifying package versions to install a specific version of a package append the version number to the package name using the at symbol for example to install a version 1.7.3 of axios you would do mpm install axios then the at symbol 1.7.3 so this command tells mpm to fetch and install the exact version of axios from the mpm register so verifying installation after installing the package it’s a good practice to verify that the correct versions have been installed you can use the mpm list and then the flag D- depth set to zero command to check the versions of the top level packages installed in your project so we can do npm list D- depth and set that to zero so this command provides a list of all packages directly installed in your project ignoring their dependencies and specifies their version numbers it allows you to quickly verify that the correct versions are installed so why specify versions the first reason is compatibility certain projects or dependencies might require specific versions to maintain compatibility breaking changes in new versions could disrupt the functionality of your application the second reason is bug fixes some versions might include bug fixes not present in newer versions or new versions might introduce bugs that were not present in previous versions and the third reason is for features older versions might have features that have been deprecated in the latest release but are still necessary for your project in conclusion understanding how to specify and install particular versions of packages with mpm is crucial for precise dependency management and software development this practice helps ensure that your application remains stable and behaves as expected regardless of changes and updates in the package ecosystem by specifying package versions you maintain control over your development en and reduce the risk of unexpected issues why might a developer need to install a specific version of an mpm package how does this practice contribute to project stability a developer might need to install a specific version of an mpm package to ensure compatibility of other dependencies maintain access to certain features or avoid bugs introduce and newer versions by specifying and controlling the exact version the developer can stabilize the project ensuring the updates or changes in the package ecosystem don’t unexpectedly break the application or alter Its Behavior this practice helps maintain a consistent and reliable development environment across different setups what are the benefits of verifying installed mpm package versions after installation and how does it ensure consistency in a nodejs project verifying installed mpm package versions after installation ensures that the correct versions are in place which is crucial for maintaining consistency across different development environments this practice helps prevent unexpected issues caused by version mismatches ensures compatibility with other dependencies and supports stable project Behavior by confirming that the specified versions are installed you can confidently manage dependencies and avoid problems that might arise from automatic updates or version conflicts [Music] so let’s go over managing outdated mpm packages maintaining the dependencies of your application ensures you benefit from the latest bug fixes performance improvements and security patches here’s how to identify and update outdated packages in your nodejs project I’ll open

up the integrated terminal so command J and I’m currently in the mpm demo directory that we created so this contains our package.json file to check which packages are outdated in your project you can use the mpm outdated command this will display all dependencies with newer versions available showing the current version you’re using the latest version available and the desired version the desired version is the highest version permitted by your versioning rules in your package.json file so currently for our project here if I view the dependencies we have installed we have axios and we have underscore both of these are currently the latest versions so I run mpm outdated nothing will show up since these are the latest possible versions to demonstrate that I’ll do mpm outdated so currently there is no result because I have the latest versions navigate outside of this directory and so if I run mpm outdated this will show the outdated packages that I have installed globally on my system so here this demonstrates the current version I have installed the desired version and the latest version so let’s go over updating packages to update old packages to the newest versions that do not include breaking changes so this typically includes minor updates and patches you can run the following command saw Run mpm update so this command updates the packages within the semantic version and constraints specified in your package.json file it will not update packages to a new major version that could contain breaking changes so let’s go over handling major updates sometimes you may need or want to update packages to their latest major versions which might include breaking changes to handle this you can use a tool called mpm check updates so let’s install that globally so I’ll use the sudu command mpm install dasg then mpm check updates I’ll enter my password so now we can run mpm check updates to see which packages have new major versions available so I can run mpm check updates you can then use the tool to update your package.json to the latest major versions so you would do mpm check updates and then the flag – or the shortcut ncu dasu so to reinstall dependencies after updating package. Json with mpm check updates the packages themselves are not automatically updated in your node modules directory you need to reinstall them to sync your directory with the updated package at Json so you can run mpm install let’s go over best practices the first best practice is testing always thoroughly test your application after updating dependencies especially when major versions are involved to ensure no breaking changes disrupt your application the second best practice is Version Control commit changes to your package.json and package lock Json file after Updates this ensures that your team or deployment environments use the same versions so in conclusion regularly updating the mpm packages in your node.js projects is crucial for maintaining the security efficiency and reliability of your applications tools like mpm check updates helps manage the life cycle of your dependencies allowing you to take advantage of the latest improvements while car carefully managing the risk of breaking [Music] changes what are the best practices for safely updating mpm packages particularly when handling major version changes best practices for safely updating mpm packages include first to review updates so use tools like mpm outdated or mpm check updates to identify and review available updates the second is to test thoroughly after updating especially when upgrading to a major version thoroughly test your application to catch any breaking changes third is to use Version Control always commit changes to package.json and package lock. Json to ensure consistency across environments and fourth update incrementally where possible update packages incrementally rather than all at once to isolate issues more easily these steps help maintain stability and minimize the risk of [Music] disruptions managing dependencies and node.js projects in node.js development it’s important to differentiate between dependencies required for the application to function and production and those needed only during the development process so let’s go over understanding dependencies first let’s consider production dependencies these are the packages your application needs to function correctly in the production environment such as Frameworks like Express or a database Library like or any other libraries necessary for the runtime execution of your app so the second type of dependency is development dependencies development dependencies are tools and libraries used only during the development process such as compilers like Babel testing Frameworks like mocha or static analysis tools like JS these are not needed in production and should not be bundled with your production build so let’s go over installing development dependencies to install a package as a development dependency use the save Dev flag this tells mpm to save the package under Dev dependencies in your package.json file this distinction is crucial for keeping production environments Lightweight by excluding unnecessary packages so we going to run the command mpm install JS hint save D so here running it in the directory that contains the package.json file and I see another property has been added named Dev dependencies which includes the package that I just specified so let’s go over the benefits of correctly categorizing dependencies the first is optimize production builds by segregating development dependencies you can ensure that your production environment only installs what is necessary reducing deployment size and potentially improving application performance the second benefit is clear project organization keeping a clear distinction between dependencies and Dev dependencies in your package.json file helps maintain organization and Clarity this makes it easier for other developers to understand the project setup managing node modules both production and development packages are stored in the node modules directory when installed the distinction in package at Json helps mpm understand which packages to install in different environments and you would use the environment variable node M and set it to development or to production so let’s discuss deploying to production when deploying your application you can ensure that only production dependencies are installed by setting the environment variable not environment to production and running mpm install mpm will skip developer dependencies in this case so in conclusion properly managing production and development dependencies is vital for efficient development workflows and optimized production deployments by categorizing your packages appropriately and package at Json you can maintain a lean an efficient application setup that ensures only necessary packages are included in production environments this practice not only optimizes performance but also enhances security by minimizing the attack surface of your [Music] application why is it important to differentiate between production and development dependencies in a nodejs project differentiating between production and development dependencies in a no. JS project is crucial because it ensures that only the essential packages needed for the application to run are included in the production environment this reduces the deployment size improves performance and minimizes security Risk by excluding unnecessary tools used only during development such as testing Frameworks or build tools proper categorization also helps maintain a clean organized project structure making it easier to manage and understand how does proper management of dependencies impact the efficiency and security of a node.js application and production proper management of dependencies in a node.js application impacts efficiency by ensuring that only necessary packages are included in the production environment reducing the application size and improving performance it also enhances security by minim minimizing the attack surface as fewer packages mean fewer potential vulnerabilities by installing only production dependencies you avoid including unnecessary tools that could introduce risk leading to a leaner more secure and optimized application and production so let’s go over uninstalling a package over time you may find that certain mpm packages are no longer needed in your application removing these packages helps keep your project lean and prevents unnecessary bloat in your no modules directory to remove an installed package you can use the mpm uninstall command followed by the package name this command removes the package from your node modules directory and updates the dependency list in your package.json file so if I wanted to remove the JS hint package that we installed in the previous lesson I can do mpm uninstall and then the name of the package so in this case JS I could also use the Shand which is mpm and then un then the name of the package so here I see my package.json file has been updated so let’s discuss the effects of uninstalling when you uninstall a package mpm automatically updates your package.json file removing the package from the list of dependencies or Dev dependencies depending on where it was listed so updating known modules the corresponding package directory and its contents are removed from the node modules folder this cleanup helps reduce the overall project size and and declutters your development environment so let’s discuss best practices the first is to verify dependencies before uninstalling a package make sure it is not required by any other part of your application you can check where and how a package is used in your project to avoid removing a package that is still in use the second best practice is to commit changes after uninstalling a package and verifying that your application still functions as expected commit the changes to your version control system this keeps your repository up toate and allows other developers to be aware of the changes and dependencies the third best practice is regular maintenance periodically check your package at Json file and your project dependencies to identify and remove packages that are no longer necessary this practice keeps your project clean and minimizes potential security risks associated with outdated or unused packages in conclusion regularly updating and cleaning up your Project’s dependencies are crucial steps in maintaining a healthy code base uninstalling unused pack P ages reduces the complexity of your project decreases lad times and lessens the risk of conflicts or security vulnerabilities by keeping your package at Json and node modules directory streamlined you ensure that your project remains efficient and [Music] manageable why is it important to regularly remove unused mpm packages from a node.js project how does this practice contribute to project maintenance regularly removing unused mpm packages from a nodejs project is important because it helps keep the project lean and efficient it reduces the size of the node modules directory improving load times and minimizing potential security risk from outdated or unnecessary packages this practice also simplifies project maintenance by reducing clutter preventing dependency conflicts and ensuring that only essential packages are included in the application keeping the coase clean and manageable enhances the overall health and stability of the project what steps should developers take before and after uninstalling mpm packages to ensure that node.js project remains functional and up toate before uninstalling mpm packages developers should verify that the package is not in use by checking where and how it is utilized in the project after uninstalling they should thoroughly test the application to ensure functions correctly without the remove package it’s also important to update the version control system by updating the changes to package. Json and package lock. Json this process ensures that the project remains functional clean and up to date so let’s go over working with global packages in node.js development some packages are not tied to a specific project but are rather tools or utilities used across multiple projects these are typically in install globally on your system so let’s go over installing Global packages first let’s discuss the purpose of global installation Global packages are typically command line tools or utilities that you want to run from anywhere on your system not just within a specific project for instance this could include package managers like mpm itself or project scaffolding tools like angler CLI which is a framework for building web applications these two packages for example are commonly installed globally to install a package globally you would use the – G or hyphen G or the– Global flag with the mpm install command this tells mpm to place the package in a special systemwide location that no JS can access from any directory so for example if you installing the angler web framework you would run the command mpm install then the flag DG and then the name of the package which is angler SL CLI this installs the angler CLI globally which you can then use to create new projects from anywhere on your system so step three is updating mpm itself mpm can also be updated globally using the same flag this is useful to ensure that you have the latest features and security updates so to do this you would run the command sudu mpm install DG mpm now a note for permissions on Mac OS and Linux you might need to use the Pudu command to install Global packages this depends on your system’s permission settings however setting up mpm to run without Pudu can avoid permission issues and is recommended for security reasons managing Global packages to manage and update your Global packages you can check which ones are outdated by running mpm outdated and then the flag – G this command lists all globally installed packages that have newer versions available upgrading Global packages if you find outdated Global packages you can update them by reinstalling with the mpm install –g command specifying the package you wish to update let’s discuss best practice IES for Global packages the first is to minimize Global installations install packages globally only when necessary overuse of global installations can lead to version conflicts between projects and complicate dependency management the second best practice is regular updates keep your Global packages updated to leverage new features and security enhancements the third best practice is to document globally installed tools for team projects document the tools required globally so all developers set up their envirment consistently in conclusion Global mpm packages are essential tools for development offering functionalities that extend across multiple projects properly managing these packages ensures that your development environment is both effective and secure by regularly updating and maintaining the global packages you can avoid potential conflicts and keep your system optimized for all your development [Music] needs what are the benefits and potential risks of installing mpm packages globally instead of locally in a node.js development environment so the benefits of global installation is that Global mpm packages are accessible from any directory on your system making them ideal for command line tools or utilities used across multiple projects such as project scaffolding tools or linters so for the potential risk overusing Global installations can lead to version conflicts between projects as different projects may require different versions of the same tool it can also complicate dependency management and make it harder to maintain consistent environments across different machines or for different team members how can developers effectively manage and maintain Global mpm packages to ensure a consistent and secure development environment developers can effectively manage and maintain Global mpm packages by following these steps the first is to minimize Global installation so only install packages globally when necessary to avoid version conflicts and simplified dependency management step two is regular updates frequently check for outdated Global packages using the mpm outdated and- G flag and update them to ensure security and access to the latest features and step three is documenting requirements clearly document any Global tools needed for a project ensuring that all team members can set up consistent and compatible environments these practices help maintain a stable and secure development environment so let’s go over publishing a package creating and Publishing your own mpm package can be a rewarding process allowing you to share your work with the wider no. JS community so to do this step one is to set up your package so let’s open up the integrated terminal and I will make a new directory and I’ll just call this new library we’ll change into this new directory so step two is to initialize the package we’ll use mpm and nit to create a package.json file with the default values so we will pass the D- yes flag which Auto accepts the default options so we can run mpm and nit D- yes so let’s create the package of Json file so we see our new directory here opening up the integrated terminal again with command J let’s scroll down so step three is to create the main file so we’ll create an index.js file where we will write the code for our package so from the command line I can do touch index.js to create that new file so we see that added here now we will add some functionality so I can say module. exports. add and I’ll assign this to a function which takes two parameters and Returns the result of adding them so a plus b and this with a semicon so now you need to create or use an mpm account so for the account setup if you don’t already have an mpm account you will need to create one this could be done from the mpm website or directly from the command line so you can run mpm add user if you already have an account and simply log in with mpm login and you will be prompted to enter your username password and email address so step three is to publish your package so to prepare for publishing ensure that your package.json file includes a unique name for your package mpm requires that package names be unique to the registry so now you’re ready to publish the package once you are ready and have verified that all information is correct you can publish your package to mpm using the command mpm publish so this command uploads your package to the mpm registry making it available for others to install so now you want to verify installation you want to test it so to ensure that your package can be installed from another project create a new directory Elsewhere on your system and install it so so for example you can do make directory and then name that directory and change into it then you can run mpm install and then that package that you created so test the functionality in this new project environment to confirm everything works as expected so after publishing you want to be sure to perform updates and maintenance so after publishing you might need to update your package with improvements or bug fixes so make changes in your local project increment the version number in your package.json file following the semantic versioning rules and run mpm publish again so now discuss metadata and visibility mpm automatically adds metadata to your publish package this includes information like the publication day version history and dependencies this metadata is crucial for users of your package to understand its history and stability in conclusion publishing a package on mpm is a straightforward process but requires careful setup and attention to detail to ensure that the package is functional and useful to others by following the steps you can contribute your own modules to the npm ecosystem and potentially help thousands of developers [Music] worldwide what are the key steps involve in creating publishing and maintaining an mpm package for the node.js community the key steps to create publish and maintain an npm package involve first setting up so create a directory initialize it with npm and nit and write your packages code step two is publishing so create or log an mpm account ensure your package name is unique and publish it using mpm publish step three is verifying so test the package by installing it in a different project to ensure it works as expected and step four is maintaining update your package as needed increment the version number and republish it to keep it current and useful for others why is it important to verify and test your mpm package after publishing and how can this impact its usability by other developers verifying and testing your mpm package after publishing is crucial to ensure it works as intended in different environments this step helps identify and fix any issues that might arise ensuring that the package is reliable and userfriendly for other developers if a package is not properly tested it can lead to errors and frustrations for users reducing its adoption and usability thorough testing enhances the package’s credibility and usefulness within the developer community so let’s go over updating a published package when you made changes to your mpm package such as adding new features or fixing bugs you must update the package’s version before republishing it this ensures that users can keep track of changes and upgrade their installations appropriately so step one is to make changes to your package so here we can modify the code so in your package directory you can make any necessary changes so for example if you wanted to add a multiplication function to your package so I can say module. exports do multiply set that to a function which takes two parameters and returns a * B so step two is to update the package version in your package.json file so here the current version is 1.0.0 and before we can publish it we need to update its version so mpm uses semantic versioning which includes major minor and Patch updates so once again the major version makes incompatible API changes the minor version adds functionality in a backwards compatible Manner and the patch version makes backwards compatible bug fixes so from the command line we can run mpm version major for breaking changes mpm version minor for new features that are backwards compatible mpm version patch for backwards compatible bug fixes so this case we can run mpm version and then minor and here we see our version has been updated in our package or Json file to be 1.1.0 this command updates the version number in your package Json and creates a new commit if your package directory is a g repository so step three is to publish the updated package so after updating the version you are now ready to publish the updated package P AG so you can run mpm publish if you try to publish without updating the version mpm will return an error because the package version must be unique following the version update the publish command should succeed additional considerations before publishing an update thoroughly test your package to ensure that new changes do not introduce bugs or break existing functionality documentation update your readme markdown file for any documentation to reflect changes made in the new version especially if You’ added new features or May significant modifications in conclusion updating a published mpm package requires careful attention to version management and compatibility by following semantic versioning rules you can communicate the nature of changes in your package updates to users effectively always ensure that your updates are well tested and documented which helps maintain and enhance the package’s utility and credibility in the community why is semantic versioning important when updating npm package how does it help communicate changes to users semantic versioning is important when updating an mpm package because it clearly communicates the type of changes made helping users understand the impact on their projects by using version numbers to indicate major breaking changes minor new features or patch bug fixes developers can manage expectations and allow users to update dependencies safely this practice ensures that users can confidently upgrade to newer versions without unexpectedly breaking their applications which best practices should developers follow when updating and republishing an mpm package to ensure its reliability and usability when updating and republishing an mpm package developers should follow these best practices the first is to use semantic versioning clearly communicate the type of changes which could be major minor or patch to users then do thorough testing ensure all new changes are well tested to prevent introducing bugs or breaking existing functionality third update documentation provid read me markdown files and other documentation to reflect the latest changes and new features then commit those changes and tag if necessary if using Version Control commit the changes and tag the new version before publishing these practices help maintain the package’s reliability and usability [Music] synchronous versus asynchronous code so let’s set up a new project we’ll open up the integrated terminal with command J or control J if you’re on Windows we’ll run the command make directory and we’ll name it async demo let’s change directory into that new folder we created now we want to initialize a new node.js project we do that with mpm anit then we’ll pass in the flag D- yes to accept the defaults just created our package.json file we clear this out now we want to create a new file we could do this from the command line and we will run touch index.js so now if we expand this directory and click into our index.js file first we will write synchronous code so we can add the following console statements we can do log and then tab for that keyboard shortcut and we’ll log out the string before so now we’ll do shift option and down arrow to copy this line and then we’ll do after so this code is a simple example of synchronous or blocking programming so here the program awaits for the first console log statement to execute and to complete before moving on to the second one we can just output this node index.js and we get our expected console log output so introducing asynchronous programming in contrast asynchronous programming allows the program to move on to other tasks before the previous ones have completed so we will modify our file here we will use the set timeout method set timeout so for the parameter we will pass in a callback function so we’re using the modern es6 syntax or eror functions So within this code block we can I’ll say a comment simulate a call to the database so let’s say we’re making a call to a database that contains information on our grocery list you can do log and we’ll say reading a grocery item from a database so for set timeout the first argument that we pass in is the call back function it also accepts a second argument which is the time to wait before executing this code this is represented in milliseconds so we’ll say 2000 represent 2 seconds and let’s execute this program so let’s open up the integrated terminal with command J up arrow and run it again so here we see before then after for our set timeout it waits 2 seconds and then it logs out this console log statement so this is an example of asynchronous programming so this demonstrates that set timeout schedules the task to be performed later without blocking the execution of subsequent code understand asynchronous programming asynchronous programming is not the same as concurrent or multi-threaded programming in OJs asynchronous code runs on a single thread it’s crucial because operations involving disk or network access in node.js are handled asynchronously allowing the program to remain responsive asynchronous programming helps ensure that your application can handle multiple operations efficiently without getting stuck waiting for one task to complete before starting another [Music] how does asynchronous programming improve the efficiency and responsiveness of a node.js application especially in handing iio operations asynchronous programming improves the efficiency and responsiveness of a node.js application by allowing the programs to continue executing other tasks while waiting for I operations such as a database call or file access to complete this non-blocking approach ensures that the application remains responsive and can handle multiple operations simultaneously rather than being helded up by slow operations as a result the application can serve more users and manage more task without delays or bottlenecks leading to better performance overall what are the key differences between synchronous and asynchronous programming in the context of node.js and why is it important for developers to understand these differences synchronous programming and node.js executes task one after the other blocking the execution of subsequent code until the current task is finished asynchronous programming on the other hand allows the program to initiate tasks like iio operations and move on to other tasks without waiting for the previous ones to complete understanding these differences is crucial because asynchronous programming helps prevent Bott necks making applications more efficient and respons by not allowing a single slow operation to Hal the entire [Music] program so let’s discuss patterns for dealing with asynchronous code let’s first go over an example of incorrect synchronous code so we’ll buildt upon the previous code snippet that we did in our previous lesson so we have our console log statement outputting before and then we call set timeout so let’s abstract this and let’s put this into a function so we use the function declaration syntax and we’ll name it get grocery item and it takes in an ID or curly braces and let’s move this so we’ll copy this and we can paste it in the block so rather than just console logging we will return a JavaScript object which contains an ID and a name so we’ll say apples is the name of the grocery item and it with a semicolon so now let’s call this function I can say cons grocery item say get grocery item and I’ll pass in the value of one is the ID let me just add a comment here so we know what to expect so we cannot get a grocery item like this as we will see then let’s do console log we will output the grocery item so note that when we do this this will have the value of undefined the reason is because when we call get grocery item the item isn’t returned immediately because we call set timeout there’s a 2C delay before we get this grocery item object let’s open up the integrated terminal up arrow and we will execute this file so here we get before undefine then we get this output after and then this console log statement within the set timeout so this function get grocery item is intended to simulate fetching an item from a database however due to the set timeout function it does not return the grocery item immediately instead it schedules the operation to occur after 2 seconds so the console log and then the grocery item executes before the grocery item data is available resulting in undefined the key reason this does not work as intended is because set timeout is asynchronous the function does not wait for 2 seconds to return the grocery item data rather it returns immediately and the code continues executing so let’s correct this approach when dealing with asynchronous operations like database calls the result is not immediately available here are three common patterns to handle a synchronous code in JavaScript the first being callbacks the second being promises and the third being a syn8 so first let’s discuss using callbacks so we will fix our code to utilize that pattern so we have our console lock statement actually let’s comment this out and we will start again from scratch so here can do console.log I’ll put the string before then we can Implement get grocery item this takes in an ID and it will accept a second parameter which is a callback function we can call set timeout and this also accepts callback function with a 2C DeLay So within it let it’s output I’ll say reading a grocery item from a database and we’ll say call back then we’ll pass in the object right the grocery item object the ID and then the name which we will say is Apple and that with the semicolon so we want to utilize the get grocery item function in its implementation it is using the asynchronous method of set timeout so we can call get grocery item pass in one as the ID and then for the call back we specify an es6 arrow function right so we’re using the modern syntax grocery item arrow and then the curly braces and here we will Define our implementation and here we will just output the GR item that is returned right so this object is passed into the call back and so this object will be the grocery item that we are outputting to the console and then one more log which is the string after so now we will execute this up Arrow so we can run this so we get before and after then it waits 2 seconds and then we see reading a grocery item from a database and then our expected grocery item object if I scroll up previously when we had our synchronous code we were outputting the grocery item and getting the value of undefined so this is a pattern known as callbacks so I’ll TR a comment here and I’ll say callbacks and for now I will comment it out and paste it so now we will update this and you will use promises so we have our console lock statement saying before and then we have the get grocery item function so rather than calling set timeout as this we can utilize a promise object so A promise is an object that holds the eventual result of an asynchronous operation so we can use the return keyword and I’ll say new promise this accepts two parameters so resolve in the case when it worked successfully and reject in the case when there was an error so this is an arrow function right so a call back we will explore each of these Concepts in more depth throughout this section just wanted to introduce it to you all at once so we moved up the set timeout to be within the Callback function now we can remove call back and rather than saying call back we say resolve because it successfully returns a grocery item so now we have to change how we’re utilizing this so we only need to pass on the ID but we have special methods in order to access the data within the promise so we use a special method which is then which is executed in the case when the promise successfully resolves so we’ll take in the item and we will console log it now we also need a method. catch let’s end this with the parthy in the case when there is an error so if there is an error in the case when it is rejected then this code will run so I’ll say console. error and then the error and that with semicolon so now open up our interor terminal we run this so we see before after and once again this waits for 2 seconds then it returns a promise so we can access the data within that promise with the then method and then we output it to the console right so explore this more in detail in future lessons for now just at a comment I’ll say promise let’s copy this and we’ll build upon it for our next example we’ll comment it out for now now we will cover async away so async away are special keywords allow us to execute this code with cleaner syntax so here we are using the then and catch methods and chaining them in order to access the data that is returned from our promise so we’ll keep our get grocery item function to be the same but we can have different syntax to make this cleaner to read so I can use a special keyword known as async which means that this function contains an asynchronous operation so I’ll name the function display grocery item so we will say grocery item then we’ll use another keyword O8 and then we will specify our function which has the asynchronous operation so in this case the set timeout function then we can simply log it out grocery item so rather than using this syntax and changing the then and do catch methods we can just call display grocery item and pass in the ID of one open up our integrated terminal run it again so we see once again before and after and once this asynchronous operation completes after 2 seconds then we successfully log it to the console let’s do a quick summary first we covered callbacks so these are functions passed as arguments to be executed once an asynchronous operation is complete Rec cover promises which are objects representing the eventual completion or failure of an asynchronous operation and lastly we covered async 08 so this is syntactic suar sugar over promises making asynchronous code look synchronous understanding these patterns is crucial for handling asynchronous operations such as database calls in [Music] JavaScript what are the main methods for handling asynchronous operations in JavaScript and why is it important to understand them the main methods for handling a synchronous oper ations in JavaScript are callbacks promises and async 08 callbacks involve passing a function to be executed after any synchronous operation completes promises represent the eventual completion or failure of an asynchronous task and provides methods like then and catch for handling results a syn8 is built on promises allowing a synchronous code to be written in a more readable synchronous like style understanding these methods is crucial for managing tasks like database calls ensuring efficient and correct code execution how does the asynchronous nature of JavaScript impact the execution order of code and what are the strategies to manage this effectively the asynchronous nature of JavaScript means that code doesn’t always execute in the order it’s written some tasks like iio operations run in the background while the rest of the code continues this can lead to unexpected result results if not managed properly to handle this developers use strategies like callbacks promises and a snle we to control the flow of asynchronous operations ensuring that tasks complete in the desired order and that results are handled correctly so let’s discuss callbacks in more detail first if you look over our example of the incorrect synchronous code where we call a function get grocery item which is utilizing set timeout with a 2-c delay when we output it we get the value undefined because the value is not immediately available so this code mimics trying to get a grocery item from a database but it doesn’t work as intended because the function get grocery item use this set timeout making it asynchronous so the console lock statement executes before the Grocer’s data is available resulting in undefined a call back is a function that is passed as an argument to another function to be executed once an asynchronous operation is complete so let’s go over use callbacks correctly so we have our updated version of the code which utilizes callback so we have our call back parameter and then we invoke it within the asynchronous operation so let’s discuss accessing nested asynchronous data so to handle multiple asynchronous operations such as fetching a user’s grocery list and then fetching the grocery item data you can Nest callbacks so here when we call get grocery item we’re currently just outputting it so let’s say we actually recalling get grocery list this takes in an ID and then a parameter which is a callback function this is an asynchronous operation so we’ll mimic that with the set timeout function pass in our Arrow function which has a 2cond delay I’ll add a comma and I’ll say simulate a call to the database log and I’ll say fetching grocery lists from the database and then we’ll utilize our call back and we’ll pass in the argument which is a JavaScript object representing the grocery list say a property of items which takes it an array so let’s say apple bananas and we’ll say bread so end that with a semic coin let’s update our G grocery item so I can say I’ll say fetching grocery item from I’ll say the grocery list just better to describe what we’re trying to implement here so I’ll say call back and we’ll say the array is apples bananas and bread so now we want to utilize get grocery list so rather than calling get grocery item we say get grocery list this accepts an ID so we’ll say one and then our call back function so it’ll be a grocery list we’ll pass an arrow function so log and I’ll Alpha grocery list comma grocery list so now I will simulate getting the grocery list items and I’ll say get grocery list items grocery list ID and then a callback function containing the items we could output that with items and then outputting that to the console and we’ll end it with a semicolon so this is an example of nested callbacks meaning that you have w a SN operation and once that completes and we have the data that we need then we make another asynchronous call utilizing that data so let’s comment this out save it and then in our integrated terminal up arrow and then run so here we get before and then after then we get fetching the grocery list and then the data that we received and then we call our nested callback function here so fetching a grocery item and we get the items so this demonstrates utilizing nested callback functions so in summary callbacks are functions passed as arguments to be executed once an asynchronous operation is complete properly handling a synchronous code is crucial when dealing with operations like database access which may take some time to [Music] complete why is it important to handle a synchronous operation properly in JavaScript particularly when dealing with tasks like database access handling asynchronous operations properly in JavaScript is crucial because it ensures that tasks like database access which may take time to complete do not block the execution of other code this allows your application to remain responsive efficiently processing multiple tasks without waiting for each one to finish sequentially proper management of a operations such as using callbacks promises or a syn away prevents issues like incomplete data retrieval or unexpected Behavior ensuring that the application functions correctly and smoothly what challenges can arise when using callbacks to manage multiple asynchronous operations and how can these be effectively addressed when using callbacks to manage multiple asynchronous operations challenges like callback hell can arise where nested callbacks make the code difficult to read and maintain this complexity increases the risk of errors and makes debugging harder to address these issues developers can use techniques such as modularizing callback functions or better yet use promises or a sync o08 syntax which allows for more readable and maintainable code by flattening the structure and handling errors more effectively so let’s further discuss nested callback structure in our previous example we use callbacks to handle asynchronous operations so we will expand upon this and we will add another asynchronous operation so we can add that with I’ll name it check item availability this will accept one parameter which is the grocery item and this utilizes the asynchronous method of set timeout pass in our call back and I’ll say checking availability then we can say return true just for Simplicity so if you want to utilize it need to do so within the get grocery item call back so we are dependent on that data this takes in you can say items at the zero index so the first item let’s clean this up a bit so you can clear this and just so we can more easily see our Nest callbacks we’ll remove the outer console log statements so here we see we have get grocery list which is an asynchronous operation once that completes then we call get grocery item which is also a synchronous and then the asynchronous method check item availability so this is simulating making calls to a backend database or a backend API so in this scenario each call back depends on the completion of the previous one resulting in a nested structure this pattern is often referred to as call back hell or the Christmas tree problem because of its shape and complexity so let’s compare this to synchronous code so just as a demonstration of what this would look like if all functions were synchronous right so it would have your log statement same before and then getting the list for get grocery list takes in the ID of the grocery list and then we get the items of the grocery list following get grocery list items say list ID then we’ll check the availability of an item check item availability and we’ll say the first item in the list then we output so log and tab after so this is an example of how clean and easy to read our code would be if it were synchronous however we know that these functions are asynchronous so the data isn’t available immediately there is a delay before we can receive that right let me just add in the 2cond delay to our callback function which I forgot to do so however synchronous code blocks the execution of other operations until the current one finishes which is not ideal for I bound tasks like database queries so let’s discuss the term of call back how we scroll back up so using callbacks for a synchronous code can become difficult to manage and read here we see our nested structure so let’s discuss a simple solution to avoid callback how we can use promises and a syn await syntax so discuss using promises promises provide a cleaner way to handle a synchronous operations so here’s an example for now we will comment how we are utilizing our asynchronous functions and rather than calling set timeout rather we will return a promise right once again A promise is an object that holds the eventual result of an asynchronous operation so we’ll say return new promise and within it it accepts a call back so we’ll say resolve for now we will close that and we can move this up we can move it up with option up Arrow close this so rather than saying call back you can remove that parameter it’s no longer needed and rather we call resolve because it resolved or completed successfully we updated this one to use promises let’s update the other functions return new promise so also accepts callback function will resolve so this here once again option up arrow and within here let’s um do command and then the right bracket better format this code we do the same here so it looks cleaner so once again we removed this call back it’s no longer needed and we call resolve it successfully Returns the grocery items now we have our last one we check availability so once again return new promise tickes in call back function with resolve then option up Arrow to move up in this case it just Returns the value true so in this case we can just say resolve we to say the value of true so now we want to utilize this so for now we can delete this example we had of syn this code and just to demonstrate what we would like the syntax to look like make some space here and now we will utilize these functions that are utilizing promises so we can call get grocery list takes in the value one then get the list and we call get grocery items TI in the list ID then we can change then right so the result of get grocery list item or get grocery item so get the items and we’ll say check item availability items at zero we’ll just say not then we’ll say availability console.log availability and then this value we also include our method or chain our method for catch in case there’s any error console.log actually we do console. eror and then the eror so this is an example of utilizing promises so we use the then method and catch methods so we are rather than having the nested structure we just chain our then methods we can execute this so up arrow and run before and after and there are two second delays as the asynchronous operations complete so everything worked as expected and we have cleaner syntax so let discuss using async AWA so the async AWA syntax built on top of promises further simp simplifies the code So currently and say in get grocery list we are returning a promise let’s say if we’re using the async away keywords so we can mark it as a sync and when we mark it as async we can now utilize the AWA function within it so rather than calling get grocery list and then changing all these methods we’ll create a new method and we can name it display availability we will mark it as a sync so once we mark it then we will utilize the AE keyword within it we’ll wrap it in a TR catch console. air and now we want to utilize these asynchronous operations so because these are asynchronous and they’re returning a promise we can use the await keyword we’ll say list AIT get grocery list pass in the ID then once this data is available then we can call wait get rery item with the list ID right so once this returns right we await this result then we check the availability await check item availability items at zero and then say [Music] console.log Avail ability and then this resolve so rather than utilizing this syntax comment this out and we’ll just call display availability so this function which utilizes the async a keywords is the equivalent of this function call with the chain methods but our code here which utilizes async away looks more similar to synchronous code so it’s easier to read so let’s run this so we see before and after 2C delay and we get our expected result with cleaner syntax so this is the modern way to do it with a SLE we so summary callbacks can lead to nested structures that are difficult to manage promises and asyn we provide cleaner more readable ways to handle asynchronous code what are the benefits of using promises and asyn a weight over callbacks in managing asynchronous operations in JavaScript using promises and a single we in Java JavaScript offers several benefits over callbacks the first being readability promises and Ayn we result in cleaner more linear code that is easier to read and maintain avoiding the nested structure of callbacks otherwise known as callback hell the second benefit is air handling promises provide better air handling through the dock catch method and TR catch blocks with the async aake keywords making it easier to manage asynchronous errors the third benefit is control flow promises and asyn weight allow for more intuitive control flow helping developers manage asynchronous operations more effectively how does the use of promises and a single weight help prevent issues like callback how in JavaScript programming the use of promises and a single weight in JavaScript helps prevent callback how by making a synchronous code more linear and easier to follow promises allow chaining of a synchronous operations with the then method instead of deeply nested callbacks while a snle way further simplifies the syntax making the code look and behave more like synchronous code this reduces complexity improves readability and makes air handling more straightforward resulting in cleaner and more maintainable [Music] code so now let’s discuss name functions so we use name functions to simplify callbacks when dealing with nested callbacks you can replace Anonymous functions with name functions to flatten and simplify the structure of your code this approach makes your code more readable and easier to manage so here’s you can refactor nested callbacks using name functions so implement this from scratch just to ensure that everything makes sense and it’s good to get more practice so once again we have our log statement say before then shift option down arrow after now we Implement our function again get grocery list takes in an ID and a call back so that’s C two parameter variables it accepts then set timeout which is an asynchronous operation the argument takes in is a callback function and here we are simulating a call to the database we can log that out so log out fetching grocery list from the database once again this calls the call back and invokes it pass in the object which is an ID and a name what is say that’s weekly groceries and that with a semicon and there is a 2cond delay so now to help us save some time we can just copy this and paste it and we’ll rename it to be get grocery items so for our console log we’ll say fetching grocery items so for our call back this accepts an array and we’ll just say milk bread and eggs as the data that we pass in once again we can copy this and paste it and we’ll name this to be check item availability so we’ll update our console lock statement which will be checking item availability so for our call back we’ll pass in a JavaScript object which will contain the item and the availability so I’ll say available set to true so now we implemented three asynchronous operations each which have a 2cond delay now in order to actually utilize this we want to have name functions so let’s Implement some functions here and I’ll call this handle grocery items this takes in a list and I’ll call get grocery items the list ID and handle item availability l so not Implement picks in the items and within it this calls check item availability so let’s say the first item and then I’ll pass in call back so display availability so now we need to implement that name function this takes in the availability this outputs to the console availability pasting that here so now I can call get grocery list the ID will be one and then for the call back I’ll say handle grocery item so that will call this function which will call get grocery items and then for the call back is handle item availability then this calls check item availability and then after within it the display availability is called logging to the console we execute this before and after then we get our 2C delays and our expected console outputs so here we see item is not defined let’s see here in checking item availability yeah so for ID it’s supposed to be item run it again now we get our expected output we just need to change the name of that parameter so explanation let’s first discuss name functions by defining name functions let’s scroll up by defining name functions like handle grocery items handle item availability and display availability you can avoid deep nesting and improve the readability of your code let’s discuss passing references note that we are passing references to these functions so this includes handle grocery items handle item availability and display availability instead of calling them directly so what are the advantages the first is readability the code is easier to read and understand the second Advantage is reusability name functions can be reused elsewhere in the code if needed limitations while using name functions helps it’s not the most efficient way to handle asynchronous code for better approach consider using promises so using promises promises provide a cleaner more manageable way to handle asynchronous operations compared to nested callbacks so here you can convert the above example to use promises so here for each of these functions that we implemented we want to call return new promise this object takes in the call back so resolve then we just move this up option up arrow and then instead of call back we just call resolve we can remove call back parameter we just repeat this so return new promise Pi in and resolve move that up option up Arrow save that and one last time oh yeah you can have to remove the call back parameter and then call result then last time we get return new promise takes in resolve and we move this up save that and we call resolve here now in order to utilize that we will no longer be calling or invoking it like that rather we will call get grocery list passing in the ID of one and then we have our methods then and catch so we chain these methods list so I know we did cover this before but repetition is very good especially if this is the first time that you are going over promises so then items and we’ll call check item availability which is the first item in the list do then say availability console.log availability and then this parameter variable then we end it with catch so we path in the error to one urse console. error and then the eror end it with a su icon so now we execute this code which is utilizing promises as opposed to callback functions we have before and after and then 2 second delays for our expected console output now we get cleaner syntax without having to pass all these references to all these functions we created so using promises makes the code more straightforward and easier to handle especially as the complexity of asynchronous operations [Music] increases how can ref factoring nested callbacks into name functions improve the readability and maintainability of asynchronous code in JavaScript refactoring nested callbacks into name functions improves the readability and maintainability of asynchronous Code by reducing complexity and avoiding deeply nested structures known as callback how name functions makes the code more organize easier to follow and allows for better reuse of code this approach simplifies debugging and understanding the flow of asynchronous operations making it easier to manage and maintain the code base as the application grows in complexity what are the limitations of using name functions for handling asynchronous operations and how do promises provide a more efficient solution the limitations of using name functions for handling asynchronous operations include increased complexity when dealing with multiple asynchronous task and a tendency to create deeply nested structures while name functions improve readability they don’t fully resolve the issue of callback how promises provide a more efficient Solution by allowing for a more linear and manageable flow of asynchronous tasks through chaining which improves readability and simplifies air handling leading to cleaner and more maintainable code so let’s discuss promises JavaScript promises are a powerful tool for managing asynchronous operations A promise is an object that represents the eventual result of an asynchronous operation it can be in one of three states the first being pending so this is the initial State when the promise is still waiting for the asynchronous operation to complete the second state is fulfilled the operation completed successfully and the promise has a value and the third possible state is rejected so the operation failed and the promise hasn’t air so Crea a promise to create a promise you can use the promise Constructor which takes a function with two parameters resolve and reject and these parameters are functions used to indicate the completion of the asynchronous operation either successfully which would be the case when it resolves or unsuccessfully in the case when it rejects so to demonstrate this say cons B and then new promise this takes in a call back so resolve and reject our Arrow function syntax then we can start in a synchronous operation such as accessing a database or calling a web service so if the operation is successful then we call resolve with the result if the operation fails then we call reject with an error so in the first case we’ll say resolve to demonstrate an example of a successful operation so output value of P and we run this we get the promise with the value of one better yet do then so we’ll say result console.log the result and we’ll just chain these methods actually so do catch error console. eror passing in that eror object so we run this again and we get the value of one which is the value that was passed in when we resolved this promise likewise if we were to call reject we pass in an error so I can say new error and I’ll say erir message in the case of a failed operation we execute this and we get our expected error message so let’s discuss consuming a promise so once you have a promise you can use theben and do catch method as we did to handle the result or the error let’s go over an example of handling errors so we’ll update this example to simulate an a synchronous operation that failed so we can call set timeout pass in call back and we’ll say it has a 2cond delay let’s move this up so option an up Arrow so now when we do this let’s update this to be console.log and we will log out the message of the air right so in this case it would be air message so now when we run this and integrated terminal command J up arrow and run there’s a 2C delay and then we get the airor message so in summary a promise starts in the pending state it transitions to fulfilled if the asynchronous operation complete successfully it transitions to rejected if the operation fails we use the DOT then method to handle the successful result and we use the catch method to handle errors finally let’s discuss best practices whenever you have an asynchronous function that takes a call back consider modifying it to return a promise for better readability and maintainability this approach helps avoid callback hell and makes the code easier to follow how do promises improve the management of asynchronous operations in JavaScript particularly compared to traditional callback methods promises improve the management of asynchronous operations in JavaScript by providing a more structured and readable way to handle tasks compared to traditional callbacks they allow you to chain operations like then for success and catch for errors handling callback hell and making the code easier to follow promises also offer better air handling and simplify the process of managing multiple asynchronous operations leading to cleaner and more maintainable code why is it beneficial to modify asynchronous operations that use callbacks to return promises instead and how does this practice enhance code readability and maintainability modifying asynchronous functions to return promises instead of using callbacks is beneficial because it simplifies the code structure making it more readable and easier to maintain promises allow for chaining operations and handling errors more cleanly with then and catch methods reducing the complexity associated with nested callbacks known as callback H this approach leads to more organized and modular code which is easier to debug and scale as your application grows so let’s discuss resolving callback outl by using promises so in this code that we wrote in a previous lesson this demonstrates nested callbacks also known as callback how which can make your code difficult to read and maintain so here in this case we have three asynchronous methods and they depend on each other so these run one after another now you can imagine if we had to perform other asynchronous operations then we will continue to have to indent and continue to Nest these callbacks so this video is just a reminder that we want to utilize promises when working with asynchronous code we we do this to improve the readability and maintainability of our code base so in this case instead of utilizing callbacks we are returning a promise right once again A promise is an object that holds the eventual result of any synchronous operation and then we can utilize the built-in methods so then and catch to chain these methods and work with the asynchronous data this approach makes the code more linear and easier to read eliminating the Deep nesting associated with callback how so in summary promises these are objects representing the eventual completion or failure of an asynchronous operation now these promises can be in different states so promises can be in one of three states so it can be pending fulfilled or rejected so methods that promises have include the then method to handle resolve values and catch to handle errors and lastly converting call back based functions to return promises can significantly improve code readability and maintainability how do promises help in resolving the challenges of callback how in a synchronous JavaScript programming promises help resolve the challenges of callback how and asynchronous JavaScript programming by allowing you to chain asynchronous operations in a more linear and readable manner instead of deeply nesting callbacks promises use then and catch methods to handle sucess sucess and errors respectively this flattens the code structure making it easier to understand maintain and debug by converting callback based functions to return promises developers can write cleaner more manageable code while avoiding the complexity and pitfalls of nested callbacks what are the key benefits of converting callback based functions to return promises particularly in terms of code readability and maintainability converting callback based functions to return promises offers key benefits in terms of code readability and maintainability Promises allow for chaining operations using then and catch which results in a flatter more linear code structure making it easier to read and understand this approach eliminates the deeply nested hardto manage code typical of callbacks known as callback how additionally promises provide a consistent way to handle errors further enhancing the maintainability of the code [Music] base so let’s go over creating subtle promises sometimes you might need to create a promise that is already resolved this can be particularly useful for unit testing where you need to simulate a successful asynchronous operation such as a web service call to create a resolve promise you can use the promise. resolve method which returns a promise that is already resolved so we can create a new file here from the command line I’ll say touch prom api.js so we can go into this new file that we created and then we can call comp P assign to promise do resolve we’ll pass in an object so in this case it will have a property of ID the value one and then to access this value we use the then method and we pass in a call back so we’ll get the result and we’ll just output that right output in the result open up the integrated terminal with command J or control J and then we will run node promise api.js and here we get the expected resolve value so this code snippet creates a resol promise with an object containing ID of one and logs the result to the console now let’s go over creating rejected promises similarly you might need to create a promise that is already rejected for instance to simulate a failed asynchronous operation in a unit test you can use the promise. reject method to create a rejected promise so we can close this out so command J and we’ll update this to instead use reject and then for the argument we pass in a new erir object so new error and then the message will be reason for rejection and three dots so now it’s p. pen we can call do cach in this case we can do error console.log and I can say error. message so because we are expecting an error or the rejection rather we just include the cach method right so we remove the then method so let’s run this and we’re expecting the error message reason for rejection say for rejection so this creates a rejected promise with an airor message and we log the air to the console so in summary resolve promises use the promise. resolve and then pass in the value to create a promise that is already resolved and for rejected promises use promise. reject and passed in an air object to create a promise that is already rejected these methods are useful for simulating different scenarios in unit tests or when you need immediate resolution or rejection of promises these methods are useful for simulating different scenarios in unit tests or when you need immediate resolution or rejection of promises how can creating resolved and rejected promises with methods like promise. resolve and promise. reject be useful in testing and simulating asynchronous operations creating resolved and rejected promises with methods like promise. resolve and promise. reject is useful in testing and simulating asynchronous operations

because they allow developers to immediately generate success or failure outcomes without needing to perform actual asynchronous task this capability is particularly valuable in unit testing where you may want to test how your code handles resolved or rejected promises such as simulating successful API responses or air conditions ensuring your code behaves correctly in different [Music] scenarios so let’s discuss running multiple asynchronous operations in parallel sometimes you need to run several asynchronous operations simultaneously and perform an action once all of them have completed for example you might call different apis like Facebook and Twitter or X and once both calls finish you return the result to the client let’s go over an example of this so we’ll have a simulation I’ll say simulation for calling Facebook API so I’ll say cons and I’ll say P1 for the first promise new promise so we know this takes in a callback takes resolve as the first parameter and within it we’ll have set timeout as our asynchronous operation this also takes a call back and we’ll say the delay is 2 seconds right so 2,000 milliseconds then we will log a say async operation Three Dots and then resolve with the value one and then we’ll have a simulation we’re calling the Twitter or X API so we’re can actually just copy this because it’ll be the same syntax just to change it to be P2 to represent the second promise I’ll say a sync operation 2 and I’ll say syn operation one just so we can differentiate these console statements so now I’ll say running both a synchronous operations let’s scroll up so we can see it better I can say promise.all and then I’ll pass it an array containing both of these promises so P1 and P2 now I’ll call then sixes s the result and I will console log the result and I also do. catch let me remove the semicolon so this takes in an err console.log and I’ll say airor air. message now we can end that with the semicon so this code kicks off two asynchronous operations and uses promise.all to wait until both promises are resolved the then method is called with the results when both operations complete so let’s execute this so command J control J and then node index.js so once both of them are completed then we see async operation one async operations 2 and then you see the two values that they return that they resolve to let me update this to be two I’ll run it again so once again we get the expected out so now let’s discuss handling promise rejections if one of the promises fail then promise.all will reject in the catch method will handle the error so if any one of them reject then the catch method will be executed so you can say for example rather than this being resolved we’ll specify the second parameter of reject and we will invoke that so this operation failed we can run that so here we see the error with the value of undefined so rather than passing one let pass in new error and I’ll say async operation one failed right for a descriptive error message rather than just the value one now we got our expected error message so in this example if P1 right the first promise right the simulation for calling the Facebook API if that fails then the entire promise.all will reject and the error will be logged so’s discuss using promise. race if you need to proceed as soon as possible as one of the promises is fulfilled or rejected you can use promise. race so rather than promise at all we can do promise. rce and in this case with promise. race the first promise to resolve or reject will determine the outcome if it resolves first the then method will be called with the result of the first fulfilled promise if it rejects first the catch method will handle the error so we can see an example of this let’s run it again so in this case the P1 rejected before the second operation likewise let’s say if I do comment this out and if I say resolve with the value one so once again promise. raise will resol or reject based on the first outcome so here we see for the result was the value of one as the async operation one completed first so in summary with promise. all this waits for all promises to resolve if any promise rejects the entire promise is rejected with promise. race this resolves or rejects as soon as one promise resolves or rejects these methods help manage multiple asynchronous operations effectively ensuring that your code is cleaner and more maintainable [Music] what are the advantages of using promise.all and promise. R for handling multiple asynchronous operations in JavaScript promise.all allows you to run multiple asynchronous operations in parallel and waits for all of them to complete before proceeding it’s useful when you need all tasks to finish successfully before taking the next step if any promise fails the entire operation fails so with promise. Ray it resolves or rejects as soon as one of the promises completes making it useful when you want to proceed based on whichever task finishes first this approach can help optimize performance when only the quickest result is needed how can managing multiple asynchronous operations with promises enhance the efficiency and readability of JavaScript applications managing multiple asynchronous operations with promises enhances the efficiency and reliability of JavaScript applications by allowing tasks to run concurrently reducing weight times with promis at all this ensures that all tasks complete successfully before proceeding making the application reliable when multiple results are needed with promise. rce this allows the application to respond Faster by acting on the first completed task improving performance in scenarios where the quickest result is prioritized these tools help structure and control complex asynchronous workflows leading to cleaner more maintainable code so let’s go over simplifying our asynchronous code with the async await keywords javascript’s async and await features provide a more readable and straightforward way to write a synchronous code resembling synchronous code so here’s an example using promises that we did in a previous lesson so here we see we have three functions which use an asynchronous operation so each of them are using set timeout and each of them return a promise so to utilize these and to get access to the result of the synchronous operation we use the then methods in order to access the data and we chain the methods now we can also implement this using the async away keywords so rather than doing it like this I can Implement a function and I’ll use the async keyword we can name this display item availability so we can say con list now we use the await keyword to await the result of the asynchronous operation we we call get grocery list we’ll pass in the ID of one then we’ll get the items say a wait get grocery items we’ll say list. name see yep so the name of the list then we’ll get the availability the await keyword check item availability so the first item in the list and then we’ll output availability and then we output the result of that so now let’s comment this out for now and we’ll just invoke this method so now if we were to execute this file need to change into the correct directory that would be nine I can run so here I get the output of after then fetching grocery list from the database fetching the grocery items and then the availability of the item so an explanation of this code we use the await keyword so this keyword allows you to wait for a promise to resolve and get its result you could use it only inside functions marked with the async keyword so let’s discuss async this keyword is used to declare that a function is asynchronous it ensures that the function returns a promise when using await the JavaScript engine pauses the execution of the function until the promise settles this makes the asynchronous code look like synchronous code which is easier to read and understand so handling errors with Ayn away in the promise based approach the catch method is used to handle errors and with a SN away you use a tri catch block so once again again we update this so I’ll say try let’s highlight all this and we’ll do option up Arrow to move it up then we can say catch air and then we can log this err out so that would be air do colon air. message better format this and then we save it so in summary asyn and wa provides a cleaner way to write a synchronous code that looks like synchronous code for for air handling we use try and catch blocks to handle errors when using a sync and a we using a sync and a we can make your asynchronous JavaScript code much more readable and easier to maintain this syntactic sugar over promises simplifies the code structure [Music] significantly how do the async and aw keywords simplify the process of writing and understanding a synchronous code in JavaScript the async and awake keywords simplify writing a synchronous code in JavaScript by making it look and behave like synchronous code async marks the function as asynchronous automatically returning a promise while await pauses the function’s execution until the promise resolves this eliminates the need for complex promise chains and nesting resulting in more readable maintainable and easier to understand code especially when dealing with multiple asynchronous operations what are the benefits of using a syn and a weight for a handling and a synchronous JavaScript code compared to traditional promise-based methods using async and a weight for error handling and JavaScript provides a more straightforward and readable approach compared to traditional promise-based methods with a SN in away you can handle errors using try and catch blocks which are familiar with synchronous code making it easier to understand and manage this approach of avoids the need for chaining catch methods resulting in cleaner code that is easier to debug and maintain especially in complex asynchronous [Music] workflows so let’s summarize what we covered in this section so this section was about synchronous versus asynchronous code understanding the difference between synchronous and asynchronous code is fundamental in JavaScript synchronous code executes sequentially blocking further execution until the current task is completed in contrast a synchronous code allows other operations to continue while waiting for an asynchronous task to complete improving performance and responsiveness let’s go over the patterns for dealing with asynchronous code JavaScript offers several patterns to manage asynchronous operations the first being callbacks these are functions passed as arguments to other functions to be invoked once an asynchronous operation is complete the second pattern is promises these are objects representing the eventual completion or failure of an a synchronous operation providing a cleaner way to handle a synchronous Logic the third pattern is a synon away this a syntax that makes a synchronous code appear synchronous enhancing readability let’s go over callbacks callbacks were the original method for handling a synchronous code in JavaScript they involve passing a function to another function to be executed after an operation completes so let’s talk about the concept of callback how these are nested callbacks which can lead to callback how which is a situation where code becomes deeply nested and difficult to manage this pattern complicates both reading and maintaining the code named functions to mitigate callback out name functions can be used to flatten the structure instead of nesting asynchronous functions you Define separate name functions and pass them as callbacks promises promises provide a more manageable alternative to callbacks a promise represents an operation that hasn’t completed yet but is expected in the future promises have three states pending fulfilled and rejected replacing callbacks with promises promises help avoid the complexity of nested callbacks by returning promises from functions you can chain asynchronous operations more straightforward using the them method for resolve promises and do catch for errors consuming promises consuming promises involves using the themm method to handle resolve values and do catch to handle errors this approach results in a more readable and maintainable code base creating subtle promises JavaScript provides promise. resolve and promise. reject methods to create promises that are already settled either fulfilled or rejected this is particularly useful in testing scenarios running promises in parallel using promise. all multiple promises can be executed in parallel and you can perform an action when all of them are resolved if any promise is rejected the entire promise. all is rejected async and a wa async and a wa keywords provide a way to write a synchronous code that look synchronous functions declared with a sync return a promise and a wait pauses the execution of the function until the promise is resolved or rejected making the code easier to read and maintain error handling is done using try and catch blocks by understanding and applying these patterns you can effectively manage asynchronous operations in JavaScript leading to more efficient and maintainable code

By Amjad Izhar
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https://amjadizhar.blog

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Modern JavaScript: Objects, Prototypes, Classes, and Modules

Node.js and JavaScript Fundamentals Study Guide

Quiz

Quiz Answer Key

Essay Format Questions

Glossary of Key Terms

Briefing Document: Asynchronous JavaScript and Module Management

Part 1: Introduction to Node.js and Development Setup

Part 2: JavaScript Fundamentals and Object-Oriented Concepts

Part 3: Module Management in Node.js

Part 4: Asynchronous JavaScript

Frequently Asked Questions on Node.js and JavaScript Asynchronous Programming

1. What are the fundamental differences between synchronous and asynchronous code execution in JavaScript, and why is understanding this distinction important for Node.js development?

2. How does Node.js utilize modules to organize and encapsulate code, and what are the advantages of this modular approach for building scalable and maintainable applications?

3. What is the Node Package Manager (npm), and why is it an essential tool for Node.js development? What are some key commands and concepts associated with npm?

4. How does Node.js handle asynchronous operations using callbacks, promises, and async/await? What are the benefits and drawbacks of each approach, and when might you choose one over the others?

5. What is the significance of the this keyword in JavaScript, and how does its behavior differ in various contexts (e.g., global scope, function context, class methods, arrow functions)? How can issues related to this context be managed?

6. Explain the concepts of closures, encapsulation, and abstraction in JavaScript. How are these principles implemented and why are they important for writing robust and maintainable code, especially in the context of object-oriented programming with Node.js?

7. What are prototypes and how does prototype-based inheritance work in JavaScript? How do constructors relate to prototypes, and why is understanding the prototype chain important for optimizing memory usage and code reuse in Node.js applications?

8. What are ES Modules and CommonJS, and how do they differ in Node.js? What are the syntaxes for importing and exporting modules in each system, and when might you choose one over the other in a Node.js project?

JavaScript OOP Challenges and Considerations

JavaScript Objects: Concepts and Mechanisms

JavaScript Object Literals: Definition and Use

JavaScript Factory Functions: Object Creation Pattern

JavaScript Constructor Functions

The Original Text

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Modern JavaScript: Objects, Prototypes, Classes, and Modules

Node.js and JavaScript Fundamentals Study Guide

Quiz

Quiz Answer Key

Essay Format Questions

Glossary of Key Terms

Briefing Document: Asynchronous JavaScript and Module Management

Part 1: Introduction to Node.js and Development Setup

Part 2: JavaScript Fundamentals and Object-Oriented Concepts

Part 3: Module Management in Node.js

Part 4: Asynchronous JavaScript

Frequently Asked Questions on Node.js and JavaScript Asynchronous Programming

1. What are the fundamental differences between synchronous and asynchronous code execution in JavaScript, and why is understanding this distinction important for Node.js development?

2. How does Node.js utilize modules to organize and encapsulate code, and what are the advantages of this modular approach for building scalable and maintainable applications?

3. What is the Node Package Manager (npm), and why is it an essential tool for Node.js development? What are some key commands and concepts associated with npm?

4. How does Node.js handle asynchronous operations using callbacks, promises, and async/await? What are the benefits and drawbacks of each approach, and when might you choose one over the others?

5. What is the significance of the this keyword in JavaScript, and how does its behavior differ in various contexts (e.g., global scope, function context, class methods, arrow functions)? How can issues related to this context be managed?

6. Explain the concepts of closures, encapsulation, and abstraction in JavaScript. How are these principles implemented and why are they important for writing robust and maintainable code, especially in the context of object-oriented programming with Node.js?

7. What are prototypes and how does prototype-based inheritance work in JavaScript? How do constructors relate to prototypes, and why is understanding the prototype chain important for optimizing memory usage and code reuse in Node.js applications?

8. What are ES Modules and CommonJS, and how do they differ in Node.js? What are the syntaxes for importing and exporting modules in each system, and when might you choose one over the other in a Node.js project?

JavaScript OOP Challenges and Considerations

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JavaScript Constructor Functions

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