This comprehensive guide covers Node.js and Express.js, starting with basic concepts like Node modules and event emitters, and progressing to building custom emitters. The material then transitions to Express.js, explaining routing, middleware, template engines, and RESTful API development, including how to create dynamic routes. It further explores REST API structure with MongoDB, including setting up a database, creating schemas, and performing CRUD operations. The guide also addresses user authentication, including registration, login, cookie management, and role-based authorization. Advanced topics like aggregation pipelines and document references in MongoDB are then discussed. Finally, the guide introduces TypeScript with Node.js, focusing on setting up a TypeScript project, using interfaces, and integrating it with Express.js and Mongoose.

Comprehensive Node.js Study Guide

Quiz

Answer each question in 2-3 sentences.

1. What is the purpose of the Node.js module system?
2. Explain the difference between module.exports and require in Node.js.
3. What is the module wrapper in Node.js, and what parameters does it include?
4. What is npm, and what are some key npm commands?
5. What does the path module provide in Node.js, and give an example of how it’s used?
6. How does the file system (fs) module work in Node.js?
7. What are streams in Node.js, and why are they useful?
8. Explain the difference between synchronous and asynchronous code execution.
9. Describe promises in JavaScript and how they are used to handle asynchronous operations.
10. What are async and await keywords used for and how do they relate to promises?

Quiz Answer Key

1. The Node.js module system allows developers to organize code into reusable pieces, promoting modularity and manageability. It allows for code to be split into multiple files and then each file can be treated as a separate module. This helps in creating large applications.
2. module.exports is used to expose functionality (variables, functions, objects) from a module, making it available for use in other modules. require is used to import the functionality that has been exported from another module.
3. The module wrapper is a function that wraps every Node.js module before it is executed, providing scope and access to module-specific variables. It includes parameters like exports, require, module, __filename (file name), and __dirname (directory name).
4. npm (Node Package Manager) is the default package manager for Node.js, used to install, manage, and publish packages. Key commands include npm init (initialize a new project), npm install (install packages), npm uninstall (uninstall packages), and npm start (run scripts defined in package.json).
5. The path module provides utilities for working with file and directory paths. For example, path.join() can be used to combine multiple path segments into a single path.
6. The file system (fs) module allows interaction with the file system, enabling operations such as reading files, writing files, creating directories, and checking file existence. Functions like fs.readFile() read from files and functions like fs.writeFile() write to files.
7. Streams in Node.js are a way to handle reading and writing data sequentially, piece by piece, instead of all at once. They are useful for processing large files or data flows efficiently, preventing memory overload.
8. Synchronous code executes line by line, with each operation completing before the next one starts, blocking the execution thread. Asynchronous code allows multiple operations to run concurrently without blocking, typically using callbacks, promises, or async/await.
9. Promises are JavaScript objects that represent the eventual completion (or failure) of an asynchronous operation. They provide a cleaner way to handle asynchronous code, avoiding callback hell and enabling better error handling through .then() and .catch() methods.
10. async is used to define asynchronous functions that implicitly return a promise, while await is used inside async functions to pause execution until a promise is resolved. This syntax makes asynchronous code look and behave more like synchronous code, improving readability.

Essay Questions

1. Discuss the advantages and disadvantages of using the Node.js module system for organizing code in large applications. How does this system compare to other module systems in languages like Python or Java?
2. Explain the concept of asynchronous programming in Node.js, detailing how callbacks, promises, and async/await are used to manage non-blocking operations. Provide examples of scenarios where asynchronous programming is essential for performance.
3. Compare and contrast the use of streams and buffers in Node.js. Describe situations where streams are preferable to buffers and explain how streams can improve the efficiency of file processing.
4. Describe the role of npm in Node.js development. Discuss the importance of package.json for managing dependencies and explain how semantic versioning is used to handle package updates and compatibility.
5. Explain how to use the module wrapper and how it allows for parameters such as require, module, filename, and dirname to be used. Give examples of each one.

Glossary of Key Terms

• Module System: A feature of Node.js that allows code to be organized into reusable units called modules.
• module.exports: A Node.js object that is used to expose functions, objects, or values from a module so they can be used by other parts of the application.
• require: A Node.js function used to import modules and their exported values into the current file.
• Module Wrapper: A function that wraps every Node.js module, providing a private scope and access to module-specific variables like exports, require, module, __filename, and __dirname.
• npm (Node Package Manager): The default package manager for Node.js, used to install, manage, and publish packages.
• npm init: An npm command that initializes a new Node.js project and creates a package.json file.
• npm install: An npm command that installs packages and their dependencies into the current project.
• npm uninstall: An npm command that removes packages from the current project.
• npm start: An npm command that runs scripts defined in the package.json file, typically used to start the application.
• package.json: A JSON file that contains metadata about a Node.js project, including dependencies, scripts, and project information.
• Path Module: A Node.js module that provides utilities for working with file and directory paths.
• File System (fs) Module: A Node.js module that provides methods for interacting with the file system, such as reading and writing files, creating directories, and checking file existence.
• Streams: A way to handle reading and writing data sequentially, piece by piece, instead of all at once.
• Synchronous Code: Code that executes line by line, with each operation completing before the next one starts.
• Asynchronous Code: Code that allows multiple operations to run concurrently without blocking, typically using callbacks, promises, or async/await.
• Promises: JavaScript objects that represent the eventual completion (or failure) of an asynchronous operation.
• async: A keyword used to define asynchronous functions that implicitly return a promise.
• await: A keyword used inside async functions to pause execution until a promise is resolved.

Node.js Development: Concepts and Practices

Okay, here’s a detailed briefing document summarizing the key themes and ideas from the provided text excerpts.

Briefing Document: Node.js Development Concepts

Overview:

This document summarizes key concepts related to Node.js development, as presented in the provided text. The excerpts cover basic syntax, module systems, package management with NPM, core modules like path and fs (file system), asynchronous programming with Promises and Async/Await, basic HTTP server creation, database interaction using Mongoose with MongoDB, project structuring, authentication with JWT, file uploads with Multer, role-based access control, testing with Jest, deployment to Render and Vercel, and GraphQL basics including schemas, queries, mutations, and resolvers. There’s also a section touching on using Typescript with Node.js.

Key Themes and Ideas:

1. Node.js Basics & Execution:

• Node.js allows execution of JavaScript code outside of a web browser environment.
• Code can be executed directly in the terminal using node <filename.js>.
• Synchronous code executes line by line. Asynchronous operations (like setTimeout) don’t block the execution of subsequent lines. “See this actually wait until unless this set timeout is getting run right so first time you’re getting this last line of the sync code and then after 2 seconds you’re getting that this message is delayed by 2 seconds.”

1. Module System:

• Node.js has a module system for organizing code into reusable pieces. “nodejs has a module system where you will be able to create different different modules and then you can use those modules in a single root module”
• Each file is treated as a separate module. “each file again I’m repeating each file in nodejs will be treated as a separate modu okay”
• module.exports is used to expose functionality from a module (similar to export in ES modules). “module. exports is used to expose functionality from a module”
• require() is used to import functionality from other modules (similar to import). “require is used to import functionality from other modules as simple as that”
• Node.js uses CommonJS module format.
• Module wrapper: Every module is wrapped in a function before execution, providing variables like exports, require, module, __filename, and __dirname. “in nodejs every module whatever module that we are creating is wrapped in a function before it executed very very important thing and this rapper function we called as a module rapper function”
• Demonstration of using module.exports and require to create and use a simple math module (first_module.js) in index.js.
• Error handling using try…catch blocks. “to do this one right let’s go here okay first I’ll just minimize this one let’s create a very try and catch block now these all are also very basic JavaScript concept so we will take a try catch and catch will give us error right here”

1. NPM (Node Package Manager):

• NPM is the default package manager for Node.js. “npm is the default package manager for nodejs”
• Allows installing and managing third-party libraries and tools.
• Manages project dependencies. “this package.json file which is nothing but a Json file that contains a metadata about your project”
• Enables running scripts defined in package.json.
• Allows publishing your own packages.
• Key NPM commands:
• npm init: Initializes a new Node.js project, creating a package.json file. “to create a new package.json inside this folder first I’m going to open in our integrated terminal and let’s close everything and here to create it so we need to do npm it”
• npm install <package_name>: Installs a specific package. “to do this one we need to use this npm install Command right so you do npm install and then the name of the package”
• npm uninstall <package_name>: Uninstalls a package.
• npm update <package_name>: Updates a package to the latest version.
• npm run <script_name>: Runs a script defined in package.json. “to run a particular script so you can see that there is different different scripts right so you need to do npm run and then the script name and whatever scripts is defined in your package. JS and so that will be automatically run”
• Distinction between dependencies (required for production) and devDependencies (needed for local development). “dependencies are all the packages that is actually required for your application to run in production”
• “the D dependencies as the name suggest only needed for your local development and in right”

1. Core Modules: Path and File System (fs)

• Path Module: Provides utilities for working with file and directory paths. “path module provides utilities for working with file and directory paths”
• path.dirname(__filename): Gets the directory name of the current file. “let’s log the current directory name so I’m going to do here console.log and let’s give like directory name right and here I’m going to give path dot so the um this is a method so this directory name and here you need to pass the file name so we’ll do file name”
• path.basename(__filename): Gets the base name (filename) of the current file.
• path.extname(__filename): Gets the file extension.
• path.join(): Joins multiple path segments into one. “I’ll create one more Sal const join path and here we are going to give path. join and you can give different path let’s I want to go to/ user and then after this I want to merge or join documents this is just example”
• path.resolve(): Resolves a sequence of paths to an absolute path.
• path.normalize(): Normalizes a path string.
• File System (fs) Module: Provides APIs for interacting with the file system. “the file system help you to work with files”
• fs.existsSync(): Checks if a file or directory exists synchronously. “I’m going to check at this FS dot so we have exists sync okay so this here we’re going to check this data folder so this will check whether this is exist or not”
• fs.mkdirSync(): Creates a directory synchronously. “fs. mkd sync now what again this will do this will create a that data folder right so I’m going to create pass your data folder and I’m going to just do a console.log and I’ll do data folder created”
• fs.writeFileSync(): Writes data to a file synchronously. ” to create a file we are going to again you need to give the file path like where you want to create the file”
• fs.readFileSync(): Reads data from a file synchronously.

1. Asynchronous Programming:

• Promises: Represents the eventual completion (or failure) of an asynchronous operation. “promise interface that we can use but let’s uh do this one with a simple example so I’m going to create a function I’m I’m going to do a delay function which will take a timer or time and this delay function will return return a promise”
• States: Pending, Fulfilled (Resolved), Rejected.
• .then(): Handles the fulfilled (resolved) state of a Promise. “this will give a DOT then right which I’m pretty sure you already know I’m you guys might be thinking that what I’m doing all of this but I think it’s important to just revise all of this one more time even if you know right so this will give you then which if the promise is getting resolv so it will come inside this then block or on full field”
• .catch(): Handles the rejected state of a Promise. ” I’m going to catch here so this will be my error block and here I’m going to just log my error and let’s do a console do log and I’m going to log my error here”
• Async/Await: Syntactic sugar over Promises, making asynchronous code easier to read and write. “asnc function that whatever each and every asnc function that you’ll be creating it will always always return a promise very very important every time it will return a promise”
• async keyword: Marks a function as asynchronous; it implicitly returns a Promise. “I’m going to do as sync function right because we need to give the ASN keyword”
• await keyword: Pauses the execution of an async function until a Promise is resolved. “the a keyword is is only be used inside your Hing function you can’t use outside of it right and what that a keyword does so it pauses the execution of the function until unless your promise is getting resolved”
• Example of creating a delay function using setTimeout and Promises, and then using async/await to call it.

1. Basic HTTP Server:

• Using the http module to create a basic HTTP server.
• Handling requests and sending responses.
• Setting response headers.
• Example of creating a simple server that responds with “Hello Node!” based on different routes.

1. MongoDB and Mongoose:

• Mongoose is an Object Data Modeling (ODM) library for MongoDB and Node.js.
• It provides a higher-level abstraction for interacting with MongoDB.
• Connecting to MongoDB:Using mongoose.connect() to establish a connection to the database. Requires a connection string (MongoDB URI).
• Error handling for connection failures.
• Defining Schemas:Using mongoose.Schema to define the structure of documents in a MongoDB collection. “if you go here first you need to create a schema right so this mongos will give you this schema property and using this you’ll be able to create a new schema so you can see that new schema and then all the properties”
• Defining data types for each field in the schema (e.g., String, Number, Boolean, Date, Array).
• Setting validation rules (e.g., required, unique). “I want to tell mongos that okay this user the whatever public will come to register in your website the enam can be only a user so it can be only a normal user or it can be a admin user”
• Setting default values for fields.
• Creating Models:Using mongoose.model() to create a model based on a schema. “this will be mongus now to create a model you need to give a model and this will take a name okay this will take a name which will be this in your database it will be stored in that particular name whatever name you give let’s say you give this one as user so this will be the collection name in your database that I I’m storing all my user in this user collection”
• Performing CRUD Operations (Create, Read, Update, Delete):create(): Creates a new document in the database.
• find(): Retrieves documents from the database.
• findById(): Retrieves a document by its ID.
• updateOne(): Updates a document in the database.
• deleteOne(): Deletes a document from the database.
• Querying Data:Using query operators (e.g., $gt for greater than, $lt for less than, $in for inclusion in an array) to filter data.
• Using logical operators (e.g., $and, $or) to combine multiple conditions.
• Sorting data using sort().
• Limiting the number of results using limit().
• Pagination using skip() and limit().
• Aggregation:Using the aggregation pipeline to perform complex data transformations. “this will be aggregation right and this aggregations pipeline actually is a concept from mangos where we can do a different set of things”
• $match: Filters documents based on specified criteria.
• $group: Groups documents based on a specified field and performs calculations (e.g., average, sum, count) on the grouped data.
• $project: Selects specific fields to include in the output documents.

1. Project Structuring:

• Importance of organizing code into a well-defined folder structure. “till this part we haven’t worked on proper folder structure right each and everything like we have created inside server.js but that is not the way so how we are going to manage our project”
• Common folder structure:
• database: Contains database connection logic (db.js).
• models: Contains Mongoose models (schemas).
• routes: Defines API routes. “each and so for example let’s say you’re having a very complex application uh where you’re having multiple you need to work with multiple collection let’s say some e-commerce project so you’ll be having products you’ll be having card you’ll be having checkout you’ll be product details so for each and everything you’ll be having different different routes so that you’re not going to write each and everything on one single file and it will become messy so that is the reason we’ll be having a routes folder right”
• controllers: Handles the main code logic for each route, interacting with the database. “controllers basically handle our main code logic that corate or basically connect with sorry not connect that uh work with your mongod database and then that controller we are going to use inside our outs”
• middleware: Contains middleware functions. “whatever middleware related Logics that we’ll be writing we are going to write inside that folder”
• helper: Contains helper/utility functions.
• .env: Stores environment variables (e.g., database URI, API keys). “why we need the NV file let’s say the mongod the mongodb URL or let’s say some sensitive information some token and everything whatever we’ll be using in our project we are not going to push those changes in our GitHub right”
• Using .gitignore to exclude sensitive files (e.g., .env, node_modules) from version control.

1. Authentication and Authorization:

• JWT (JSON Web Token):Using JWT for user authentication. “we need to authenticate every request by by passing a JWT token and then check if it’s a authenticated or not”
• Generating a JWT upon successful login. “if those condition meets then we create our GWT token so that can access their route that’s it now this is like a very simple but the whole entire work how the authentication and authorization work behind the scene it”
• Verifying the JWT in middleware to protect routes. “it that okay this will be a our security so we’ll be passing something and based on that we be able to check the data”
• jsonwebtoken library for creating and verifying JWTs.
• bcrypt.js:Hashing passwords before storing them in the database. “we need to has it or we need to store in encrypted form so that is the reason we’re going to use this most used package and that is called the bcrypt JS what this does you can see that it will create a Sol to protect against your Rainbow table attacks”
• Comparing hashed passwords during login.
• Using bcrypt.hash() to hash a password.
• Using bcrypt.compare() to compare a password with its hash.
• Role-Based Access Control (RBAC):Implementing RBAC to restrict access to certain routes based on user roles (e.g., admin, user). “So role based authentication or access control actually means what let’s say if there is a admin panel so you can only able to see if you are an admin user okay if you are a normal user it might be you’re not able to see”
• Adding a role field to the user schema.
• Creating middleware to check user roles before granting access to routes.

1. File Uploads with Multer:

• Using Multer middleware to handle file uploads.
• Configuring Multer to specify the storage location for uploaded files.
• Handling single and multiple file uploads.
• Storing file information in the database.
• Cloudinary is an option for file storage

1. Testing with Jest:

• Using Jest for writing unit tests. “let’s see that we’re going to how we are going to write some test okay so we’re going to use J and also the super test right and using these two package we we are going to write API test now as I already told you that what the unit test unit tests actually helps you to create the test for each and individual method not method each and individual modules it will not trigger any other modules it just want to test a single unit that’s what it”
• Writing test cases to verify API endpoints.
• supertest for sending HTTP requests to the API during testing.
• Using expect() to make assertions about the response.

1. Deployment (Render and Vercel):

• Deploying Node.js applications to cloud platforms like Render and Vercel.
• Render:Creating a render.yaml file to configure the deployment.
• Specifying the build command and start command in the render.yaml file.
• Setting environment variables in the Render dashboard.
• Vercel:Configuring the build and output options in the Vercel dashboard.
• Setting environment variables in the Vercel dashboard.
• Importance of modifying package.json to ensure correct deployment.

1. GraphQL:

• GraphQL is a query language for APIs (developed by Facebook). “graph kill is developed by Facebook and uh this is nothing just a query language for apis”
• Advantages over REST:
• Precise data fetching: Clients can request only the data they need.
• Single endpoint for all data operations.
• Improved performance due to reduced over-fetching and under-fetching.
• Key GraphQL concepts:
• Schema: Defines the structure of the data and the operations that can be performed. “the schema file will Define your schema for your project that you are creating now what actually that schema is that is nothing but the structure of your data or the operation that you will perform”
• Types: Define the data types of the fields in the schema (e.g., String, Int, Float, Boolean, ID). “this type keyword you need to give and then the name so let’s give this one as product so this is your type now inside this you need to specify that what kind of fields this product will have”
• Queries: Used to fetch data.
• Mutations: Used to modify data (create, update, delete). “mutation is where we’ll be able to create create a new product”
• Resolvers: Functions that provide the data for the fields in the schema. “resolvers simply resolve what you are going to do so how you’re going to face the data”
• Using graphql-tag to write GraphQL schemas and queries.

1. TypeScript with Node.js:

• Using TypeScript to add static typing to Node.js applications. “TypeScript is what it’s a superet of Javascript and that is actually what it has a static typing so whenever you’ll be creating projects you might uh or you usually wanted to write your function or the properties with a specific types”
• Benefits of using TypeScript:
• Improved code readability and maintainability.
• Early detection of errors during development.
• Better code completion and refactoring support in IDEs.
• Defining interfaces to specify the types of objects. “you can create custom types remember I created this custom request and then I extend the request object from Express similarly for this one also you can extend the main document and then you can add your own Uh custom uh schemas or user structure whatever you you will be creating here”
• Typing Mongoose schemas and models.

Overall Impression:

The text provides a broad overview of essential Node.js development concepts, ranging from basic syntax and module management to advanced topics like asynchronous programming, database interaction, testing, deployment, and GraphQL. The excerpts emphasize the importance of code organization, proper error handling, and understanding the underlying principles of each technology.

Node.js Development: Frequently Asked Questions

Frequently Asked Questions about Node.js Development

Here are some frequently asked questions, based on the provided documentation.

1. What is the Node.js module system, and why is it important?

The Node.js module system allows you to organize your code into reusable pieces. Instead of writing all code into one large file, you can break it down into separate modules (files). This modularity makes code more manageable, readable, and reusable, particularly in large applications. Each file in Node.js is treated as a separate module. The module system relies on module.exports (to expose functionality from a module) and require (to import functionality from other modules).

2. How do module.exports and require work in Node.js?

module.exports is used to expose functions, objects, or values from a Node.js module, making them available for use in other modules. Think of it like ‘export’ in ES modules. require is used to import the functionality that has been exposed by other modules via module.exports. It’s similar to ‘import’ in ES modules, but follows the CommonJS syntax used by Node.js. When you require a module, you get whatever was assigned to module.exports in that module.

3. What is the module wrapper in Node.js?

In Node.js, every module’s code is wrapped inside a function before execution. This wrapper function provides several arguments: exports, require, module, __filename (the current file’s name), and __dirname (the current directory’s name). This wrapper provides a level of privacy and encapsulation for the module’s code, preventing variables and functions from polluting the global scope.

4. What is npm (Node Package Manager), and what are some essential commands?

npm is the default package manager for Node.js. It allows you to install, manage, and publish Node.js packages (libraries and tools). Key npm commands include:

• npm init: Initializes a new Node.js project and creates a package.json file. Using npm init -y automatically accepts the defaults and creates a package.json file without prompting for input.
• npm install <package_name>: Installs a specific package as a dependency for your project.
• npm uninstall <package_name>: Uninstalls a package from your project.
• npm update <package_name>: Updates a package to the latest version.
• npm run <script_name>: Runs a script defined in the package.json file.

5. What is the purpose of package.json?

The package.json file is a JSON file that contains metadata about your Node.js project. It lists project dependencies (packages required for the application to run), development dependencies (packages needed only for development, like testing tools), scripts (commands to automate tasks), and other project-related information.

6. How does the path module in Node.js help with file paths?

The path module provides utilities for working with file and directory paths. It offers functions to:

• Get the directory name of a file (path.dirname()).
• Extract the base name (file name) from a path (path.basename()).
• Get the file extension (path.extname()).
• Join multiple path segments into a single path (path.join()).
• Resolve a path to an absolute path (path.resolve()).
• Normalize a path to remove redundant separators (path.normalize()).

7. How do you handle asynchronous operations in Node.js using Promises, async, and await?

• Promises: Promises represent the eventual result of an asynchronous operation. They can be in one of three states: pending, fulfilled (resolved), or rejected. Promises provide a structured way to handle asynchronous code, avoiding callback hell. You can use .then() to handle successful resolutions and .catch() to handle rejections.
• Async/Await: async and await are syntactic sugar over Promises, making asynchronous code look and behave more like synchronous code. An async function always returns a Promise. The await keyword can only be used inside an async function and pauses the execution of the function until a Promise is resolved or rejected. This makes asynchronous code easier to read and write.

8. How can you connect to a MongoDB database using Mongoose and define a schema?

First, install the Mongoose package (npm install mongoose). Then, use mongoose.connect() to connect to your MongoDB database, providing the connection URL. After the connection is successful, define a schema using new mongoose.Schema(), specifying the data types and properties for each field in your documents. Then use mongoose.model() to create a model. This model allows you to interact with your MongoDB database collection using Mongoose’s methods (e.g., find(), create(), save(), delete(), aggregate())

Node.js Custom Event Emitter Guide

A custom event emitter can be created in Node.js using the events module. Here’s how it works:

1. Import the events module.

• This module is required to create event emitters.
• const eventEmitter = require(‘events’).

1. Create a class that extends EventEmitter.

• This class will serve as the custom event emitter.
• It inherits the emit and on methods from the EventEmitter class.
• class MyCustomEmitter extends eventEmitter {
• constructor() {
• super();
• this.greeting = ‘Hello’;
• }
• greet(name) {
• this.emit(‘greeting’, this.greeting, name);
• }
• }

1. Define a constructor.

• The constructor can be used to set up initial properties for the emitter.
• It calls super() to invoke the constructor of the parent class (EventEmitter).
• In the example, the greeting property is initialized.

1. Create a method to emit events.

• This method uses the emit method to trigger an event with a specific name.
• It can also pass arguments to the listeners.
• In the example, the greet method emits a greeting event with the greeting and a name.

1. Create an instance of the custom emitter.

• This creates an object that can emit and listen for events.
• const myCustomEmitter = new MyCustomEmitter();

1. Register a listener for the event.

• The on method is used to register a listener function that will be executed when the event is emitted.
• The listener function receives the arguments passed by the emit method.
• myCustomEmitter.on(‘greeting’, (greeting, name) => {
• console.log(‘Greeting event:’, greeting, name);
• });

1. Emit the event.

• Call the method that emits the event to trigger the listener function.
• myCustomEmitter.greet(‘Sumit’);

When the code is executed, the greet method emits the greeting event. This triggers the listener function, which logs “Greeting event: Hello Sumit” to the console.

Creating an Express Server in Node.js

An Express server in Node.js can be created as follows.

Key Features of Express.js

• Routing: Express.js is known for its routing capabilities.
• Middleware: It uses middleware.
• Template Engines: It supports template engines like EJS and Pug for dynamic HTML generation.
• Static File Serving: It can serve static files.
• Error Handling: It offers error handling.
• RESTful API Development: It is useful for creating RESTful APIs.

Steps to Create an Express Server

1. Import the Express module: This is done using the require function.
2. const express = require(‘express’);
3. Create an Express application: Invoke the express module which returns an express application.
4. const app = express();
5. Define a port to listen for client requests.
6. const port = 3000;
7. Create routes: Define routes for different HTTP methods (GET, POST, etc.) and URL paths.
8. app.get(‘/’, (req, res) => {
9. res.send(‘Hello World!’);
10. });

• The app.get() method specifies a route for handling GET requests to the root URL (“/”).
• The callback function receives a request object (req) and a response object (res).
• The res.send() method sends the response “Hello World!” back to the client.

1. Start the server: Use the app.listen() method to start the server and listen for incoming connections on a specific port.
2. app.listen(port, () => {
3. console.log(`Server is running at port ${port}`);
4. });

• This makes the server accessible at localhost:3000.

Middleware

• To use middleware, the app.use() method is employed.
• Middleware functions have access to the request and response objects, and the next middleware function in the stack.
• express.json() is a built-in middleware used to parse JSON data in request bodies.

Application Settings

• app.set() is used to set application-level settings, such as the view engine.
• For example, to set the view engine to EJS:
• app.set(‘view engine’, ‘ejs’);

Example

const express = require(‘express’);

const app = express();

const port = 3000;

app.get(‘/’, (req, res) => {

res.send(‘Hello World!’);

});

app.listen(port, () => {

console.log(`Server is running at port ${port}`);

});

Express.js Dynamic Routing

Dynamic routing in Express.js involves creating routes where a portion of the URL can vary. This allows a single route to handle requests for multiple resources based on a parameter passed in the URL.

Key Concepts and Implementation

• Defining Dynamic Routes: To create a dynamic route, a colon (:) is used before the parameter name in the route path. For example, /products/:id defines a route where :id is a dynamic parameter.
• Accessing Route Parameters: The req.params object is used to access the values of the dynamic parameters. For example, in the route /products/:id, the value of id can be accessed using req.params.id.
• Example:
• app.get(‘/products/:id’, (req, res) => {
• const productID = parseInt(req.params.id); // Parse the ID
• // Logic to retrieve product from a database or array
• // Send the product as a JSON response
• });

Note: Information regarding retrieving a product from a database or array was not found in the source.

Use Cases

• E-commerce Applications: Dynamic routes are commonly used in e-commerce to display details for specific products. For example, clicking on a product with id2 would navigate to /products/2.
• API Endpoints: They are useful for creating API endpoints where a specific resource needs to be accessed based on its ID or another identifier.

Important Notes

• Parameter Naming: When defining dynamic routes, the name given to the parameter after the colon (e.g., :id) must be used to access its value in req.params (e.g., req.params.id).
• Data Retrieval: In real-world scenarios, the dynamic value captured from the URL is often used to query a database and retrieve the corresponding data.
• Middleware: Dynamic routes can also be used with middleware to perform actions based on the parameters.

By using dynamic routing, Express.js applications can create more flexible and efficient routes that adapt to different request parameters.

Express.js Template Engines for Dynamic HTML Generation

Template engines in Express.js are used to generate dynamic HTML pages with plain JavaScript. Template engines can help to generate dynamic HTML pages in Express applications.

Key Aspects

• Definition: A template engine is HTML markup with plain JavaScript.
• Purpose: Template engines help in generating dynamic HTML pages in Express applications.

Example with EJS

• Set the View Engine: Tell Express to use EJS as the view engine.
• app.set(‘view engine’, ‘ejs’);
• Set the Views Directory: Specify the directory where the view files are located.
• app.set(‘views’, path.join(__dirname, ‘views’));
• Create Views: Create a views folder where the HTML files will reside. Each file in this folder will be treated as a separate module.
• Render Views: Use res.render() to render the template and pass data to it.
• app.get(‘/’, (req, res) => {
• res.render(‘home’, { title: ‘Home’, products: products });
• });
• In this example, home.ejs is rendered, and data such as title and products are passed to the template.
• Access Data in Templates: Use special tags to output dynamic values in the template.
• <h1><%= title %></h1>
• <ul>
• <% products.forEach(product => { %>
• <li><%= product.title %></li>
• <% }); %>
• </ul>
• The <%= … %> tag is used to output the value of a variable.
• The <% … %> tag is used for control flow, such as loops.

Benefits of Using Template Engines

• Dynamic HTML: Template engines allow generating HTML pages dynamically based on data from the server.
• Code Reusability: Common components, like headers and footers, can be created as partials and included in multiple views.

By using template engines like EJS, developers can create dynamic and maintainable web applications with Express.js.

RESTful API Development with Express.js: A Practical Guide

RESTful API development involves creating APIs that adhere to the principles of REST (Representational State Transfer) architecture. Express.js is a framework that provides features for building such APIs in Node.js.

Key Features of Express.js for API Development

• Routing: Manages routes.
• Middleware: Uses middleware.
• RESTful API Development: Facilitates RESTful API creation.

Project Structure

To organize an API project, a typical structure includes:

• Models: Data models for interacting with the database.
• Controllers: Logic for handling requests and responses.
• Routes: Defines the API endpoints.

Steps to Build a RESTful API

1. Set up the project: Create a new Node.js project and initialize package.json.
2. npm init -y
3. Install Express.js: Install Express.js and any other required packages such as body-parser.
4. npm install express
5. Create the main application file: Create app.js (or a similar name) to set up the Express server.
6. Require Express: Import the Express module.
7. const express = require(‘express’);
8. Create an Express application: Invoke express to create an application.
9. const app = express();
10. Define middleware: Use middleware to parse JSON data.
11. app.use(express.json());
12. Define routes: Create routes for different API endpoints.

• GET: Retrieve data.
• app.get(‘/api/books’, (req, res) => {
• // Logic to get all books
• });
• app.get(‘/api/books/:id’, (req, res) => {
• // Logic to get a single book by ID
• });
• POST: Create new data.
• app.post(‘/api/books’, (req, res) => {
• // Logic to add a new book
• });
• PUT: Update existing data.
• app.put(‘/api/books/:id’, (req, res) => {
• // Logic to update a book
• });
• DELETE: Delete data.
• app.delete(‘/api/books/:id’, (req, res) => {
• // Logic to delete a book
• });
• Dynamic routes can be created using colons to define parameters.

1. Start the server: Specify the port and start listening.
2. const port = 3000;
3. app.listen(port, () => {
4. console.log(`Server is running on port ${port}`);
5. });

Testing APIs with Postman

• Install Postman: Download and install Postman for testing API endpoints.
• Create requests: Set up requests in Postman to test each route.
• Specify the type (GET, POST, PUT, DELETE).
• Enter the URL.
• Include any required headers or body data.
• Send requests and verify responses: Send the requests and verify that the responses are as expected.

By following these steps, you can create a RESTful API using Express.js, organize the project structure, and test the API endpoints with Postman.

By Amjad Izhar
Contact: amjad.izhar@gmail.com
https://amjadizhar.blog

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