Tutorials | Express Js

1. Introduction to Express.js:

Express.js is a minimal and flexible Node.js web application framework that provides a robust set of features for developing web and mobile applications. It is designed to make it easier to build web applications and APIs by providing a simple and expressive syntax.

Key features and characteristics of Express.js include:

Middleware: Express.js uses middleware functions that have access to the request and response objects. Middleware functions can perform various tasks such as modifying the request and response objects, terminating the request-response cycle, or calling the next middleware in the stack.
Routing: Express.js provides a simple and effective way to define routes for handling different HTTP methods (GET, POST, PUT, DELETE, etc.) and URL patterns. Route definitions are organized, making it easy to manage the application’s structure.
Templating Engines: While Express.js itself does not include a templating engine, it can be easily integrated with popular templating engines like EJS, Pug, and Handlebars to generate dynamic HTML content on the server.
Middleware for Handling HTTP Requests and Responses: Express.js simplifies handling HTTP requests and responses by providing built-in middleware for parsing request bodies, handling cookies, serving static files, and more.
Error Handling: Express.js has built-in error-handling middleware that can be used to handle errors that occur during the request-response cycle. Custom error handling can also be implemented.
Routing and URL Parameters: Express.js allows developers to define routes with parameters, making it easy to capture values from the URL. This enables the creation of dynamic routes.
HTTP Methods and RESTful APIs: Express.js supports various HTTP methods, making it well-suited for building RESTful APIs. It simplifies the process of handling different HTTP verbs and managing resource endpoints.
Modularity: Express.js applications can be organized into modular components called routers. Routers enable developers to create modular and reusable code for different parts of an application.
Integration with Middleware Libraries: Express.js can be extended and customized through the use of middleware libraries. Popular middleware libraries exist for tasks such as authentication, logging, and security.
Active Community: Express.js has a large and active community, which means a wealth of resources, tutorials, and third-party modules are available. This community support makes it easier for developers to find solutions to common problems.

Hello World Example:

Here is a simple example of an Express.js application:

const express = require(‘express’);
const app = express();
const port = 3000;

app.get(‘/’, (req, res) => {
res.send(‘Hello, Express.js!’);
});

app.listen(port, () => {
console.log(`Server listening on port ${port}`);
});

This example creates a basic Express.js application that listens on port 3000 and responds with “Hello, Express.js!” when a request is made to the root URL (“/”).

2. Setting Up Express.js:

Setting up an Express.js application involves a few steps to get your project structure organized, install necessary dependencies, and create a basic server file. Below is a step-by-step guide to set up a simple Express.js application.

1. Create a Project Directory:

Create a new directory for your Express.js project. Open your terminal or command prompt and run the following commands:

mkdir my-express-app

cd my-express-app

2. Initialize the Project:

Run the following command to initialize a new Node.js project. This will create a package.json file where you can specify project details and dependencies.

npm init -y

3. Install Express.js:

Install the Express.js framework by running the following command:

npm install express

4. Create a Server File:

Create a new file (e.g., app.js or server.js) in your project directory to define your Express application.

// app.js or server.js
const express = require(‘express’);
const app = express();
const port = 3000;

app.get(‘/’, (req, res) => {
res.send(‘Hello, Express!’);
});

app.listen(port, () => {
console.log(`Server is running on http://localhost:${port}`);
});

This simple Express application responds with “Hello, Express!” when you access the root URL (http://localhost:3000/).

5. Run Your Express App:

Run your Express application using the following command:

node app.js

Visit http://localhost:3000/ in your web browser, and you should see the “Hello, Express!” message.

Additional Steps (Optional):

Nodemon for Auto-Restart:
- Install nodemon globally to automatically restart your server when changes are made.
  npm install -g nodemon
- Use nodemon to run your server:
  nodemon app.js
Express Generator (For Scaffold):
- Install express-generator globally to generate a scaffold for your Express application.
  npm install -g express-generator
- Create a new Express application using the generator:
  express my-express-app cd my-express-app npm install
- Run your application:
  npm start

Express Generator provides a more structured project with predefined folders and files.

With these steps, you have set up a basic Express.js application. You can now start building your routes, middleware, and expand your application based on your project requirements.

3. Routing in Express:

To modularize your routes, you can use the express.Router middleware. This allows you to define routes in separate files and then mount them in your main application.

Create a file userRoutes.js:

const express = require(‘express’);
const router = express.Router();

router.get(‘/’, (req, res) => {
res.send(‘User Home Page’);
});

router.get(‘/:userId’, (req, res) => {
const userId = req.params.userId;
res.send(`User ID: ${userId}`);
});

module.exports = router;

In your main application file:

const express = require(‘express’);
const app = express();
const userRoutes = require(‘./userRoutes’);

// Mount the userRoutes at /users
app.use(‘/users’, userRoutes);

app.listen(3000, () => {
console.log(‘Server is running on http://localhost:3000’);
});

Now, /users and /users/:userId routes are defined in a separate file.

4. Middleware in Express:

Middleware functions in Express.js are functions that have access to the request object (req), the response object (res), and the next middleware function in the applicationâs request-response cycle. Middleware functions can perform various tasks such as modifying request and response objects, terminating the request-response cycle, and calling the next middleware in the stack.

Built-in Middleware:

Express.js provides several built-in middleware functions that can be used in an application. Some common examples include:

express.json() and express.urlencoded() for Parsing Request Bodies:
- Parse incoming request bodies in JSON and URL-encoded formats.
const express = require(‘express’);
const app = express();
app.use(express.json());
app.use(express.urlencoded({ extended: true }));
express.static() for Serving Static Files:
- Serve static files such as images, CSS, and JavaScript.
const path = require(‘path’);
app.use(express.static(path.join(__dirname, ‘public’)));
Logger Middleware:
- Implement a custom middleware for logging.
app.use((req, res, next) => { console.log(`[${new Date().toISOString()}] ${req.method} ${req.url}`); next(); });

Custom Middleware:

Developers can create custom middleware functions to perform specific tasks. Middleware functions are executed in the order they are defined in the application code.

// Custom middleware function
const myMiddleware = (req, res, next) => {
// Perform some tasks
console.log(‘Custom middleware executed’);
next(); // Call the next middleware in the stack
};

// Use the custom middleware
app.use(myMiddleware);

// Define a route
app.get(‘/’, (req, res) => {
res.send(‘Hello, Express!’);
});

Error Handling Middleware:

Middleware functions can also be used for error handling. If an error occurs during the request-response cycle, the error-handling middleware is invoked.

// Error handling middleware
app.use((err, req, res, next) => {
console.error(err.stack);
res.status(500).send('Internal Server Error');
});

Route-Specific Middleware:

Middleware can be applied to specific routes, allowing developers to selectively enable or disable middleware for different parts of the application.

// Middleware for a specific route
const routeMiddleware = (req, res, next) => {
console.log(‘Middleware for a specific route’);
next();
};

// Apply middleware to a specific route
app.get(‘/special-route’, routeMiddleware, (req, res) => {
res.send(‘Special Route’);
});

Third-Party Middleware:

Express.js supports the use of third-party middleware for various functionalities. Examples include morgan for logging, helmet for securing HTTP headers, and compression for response compression.

const morgan = require(‘morgan’);
const helmet = require(‘helmet’);
const compression = require(‘compression’);

// Use third-party middleware
app.use(morgan(‘combined’));
app.use(helmet());
app.use(compression());

Middleware plays a crucial role in Express.js applications by allowing developers to customize the request-response cycle and add functionalities to their applications. Understanding how middleware works is essential for building robust and modular web applications.

5. Express Application Generator:

The Express Application Generator is a command-line tool provided by Express.js to quickly scaffold the basic structure of an Express.js application. It sets up the project with a default directory structure, configuration files, and an initial server setup. This tool is useful for getting started with an Express.js project without manually creating all the boilerplate code.

Here are the steps to use the Express Application Generator:

1. Install Express Generator Globally:

You need to install the Express Generator globally using npm. Open your terminal or command prompt and run the following command:

npm install -g express-generator

2. Generate an Express App:

After installing the generator, you can use it to create a new Express.js application. Navigate to the directory where you want to create your project and run the following command:

express my-express-app

Replace my-express-app with the desired name of your project.

3. Navigate to the Project Directory:

Change into the newly created project directory:

cd my-express-app

4. Install Dependencies:

Run the following command to install the project dependencies:

npm install

5. Start the Express App:

Now, you can start your Express.js application with the following command:

npm start

Alternatively, you can use the npm run dev command to start the application with nodemon, which automatically restarts the server when changes are detected.

Project Structure:

The generated project structure includes the following directories and files:

my-express-app/
|-- bin/
| |-- www
|-- public/
| |-- images/
| |-- javascripts/
| |-- stylesheets/
| |-- style.css
|-- routes/
| |-- index.js
| |-- users.js
|-- views/
| |-- error.pug
| |-- index.pug
| |-- layout.pug
|-- app.js
|-- package.json

bin/www: Entry point for the application, starting the server.
public/: Static files (images, stylesheets, JavaScript) that can be served by Express.
routes/: Contains route files. By default, there are index.js and users.js.
views/: Template files, by default in Pug format.
app.js: Main application file where you configure and set up the Express application.

Customizing Templates:

By default, Express Generator uses the Pug templating engine. If you prefer a different template engine, you can specify it during project generation. For example, to use the EJS templating engine:

express --view=ejs my-express-app

Replace ejs with your preferred template engine.

With the Express Application Generator, you can quickly set up a basic Express.js application and start building your project without the need to create the initial project structure manually.

6. Handling Forms and Parsing Data:

Handling forms and parsing data in an Express.js application involves capturing and processing data submitted through HTML forms. Here’s a step-by-step guide on how to handle forms and parse data in an Express.js application:

1. Set Up Your Express App:

Ensure you have an Express.js application set up. You can create one using the Express Application Generator or manually set up a basic Express app.

2. Create an HTML Form:

Create an HTML form in one of your views. For example:

<!-- views/form.html -->
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Sample Form</title>
</head>
<body>
<h1>Submit a Form</h1>
<form action="/submit" method="post">
<label for="name">Name:</label>
<input type="text" id="name" name="name" required>
<br>
<label for="email">Email:</label>
<input type="email" id="email" name="email" required>
<br>
<button type="submit">Submit</button>
</form>
</body>
</html>

3. Install Necessary Dependencies:

You’ll need the body-parser middleware to parse form data. Install it using:

npm install body-parser

4. Configure Express to Use `body-parser`:

In your Express app, configure the body-parser middleware:

const express = require(‘express’);
const bodyParser = require(‘body-parser’);

const app = express();
const port = 3000;

app.use(bodyParser.urlencoded({ extended: true }));
app.use(express.static(‘public’)); // Serve static files if needed

// Your routes and other configurations go here

app.listen(port, () => {
console.log(`Server is running on http://localhost:${port}`);
});

5. Handle Form Submission:

In your Express app, create a route to handle the form submission:

app.post('/submit', (req, res) => {
const { name, email } = req.body;
res.send(`Form submitted with Name: ${name}, Email: ${email}`);
});

6. Test Your Form:

Start your Express app:
node app.js
Visit http://localhost:3000/form in your browser, fill out the form, and submit it.
Check the console logs and the response to see the submitted form data.

This example demonstrates the basic setup for handling forms and parsing data in an Express.js application. Depending on your application’s needs, you might want to add validation, sanitize user input, or connect to a database to store the form data. Adjustments can be made based on your specific requirements.

7. Express Routers:

Express routers are a way to modularize and organize routes in an Express.js application. Routers allow you to split your application into smaller, more manageable parts, making it easier to maintain and scale. Each router instance is like a mini Express application with its own routes, middleware, and settings.

Here’s a step-by-step guide on how to use Express routers:

1. Create a New Router File:

Create a new file for your router, for example, userRoutes.js. Inside this file, you can define the routes specific to user-related functionality.

javascript

// userRoutes.js
const express = require(‘express’);
const router = express.Router();

// Define routes for users
router.get(‘/’, (req, res) => {
res.send(‘User Home Page’);
});

router.get(‘/profile’, (req, res) => {
res.send(‘User Profile Page’);
});

module.exports = router;

2. Use the Router in Your Main Application:

In your main application file (e.g., app.js or server.js), use the router by requiring and mounting it:

javascript

const express = require(‘express’);
const userRoutes = require(‘./userRoutes’); // Import your router

const app = express();
const port = 3000;

// Mount the userRoutes at /users
app.use(‘/users’, userRoutes);

// Your other routes and configurations go here

app.listen(port, () => {
console.log(`Server is running on http://localhost:${port}`);
});

3. Test Your Routes:

When you run your application and visit http://localhost:3000/users or http://localhost:3000/users/profile, the corresponding routes defined in the userRoutes file will be matched.

4. Additional Router Features:

Router Middleware: You can use middleware specific to the router by adding it to the router instance.
router.use((req, res, next) => { console.log('Middleware for the userRoutes'); next(); });
Router Parameters: You can define parameters for routes within the router.
router.get('/:userId', (req, res) => { const userId = req.params.userId; res.send(`User ID: ${userId}`); });
Sub-Routers: You can use sub-routers within a router file to further organize your code.
javascript
// userRoutes.js
const express = require(‘express’);
const router = express.Router();
const profileRouter = require(‘./profileRouter’);
// Mount the profileRouter at /profile
router.use(‘/profile’, profileRouter);
module.exports = router;

5. Sub-Routers:

You can also have sub-routers, which are routers mounted within other routers. This is useful for creating a hierarchical structure for your routes.

javascript

// profileRouter.js
const express = require(‘express’);
const router = express.Router();

router.get(‘/’, (req, res) => {
res.send(‘Profile Page’);
});

module.exports = router;

// userRoutes.js
const express = require(‘express’);
const router = express.Router();
const profileRouter = require(‘./profileRouter’);

router.use(‘/profile’, profileRouter);

module.exports = router;

This way, you can have a clear and organized structure for your routes by using Express routers, making your application more modular and easier to manage as it grows.

8. RESTful APIs with Express:

Creating RESTful APIs with Express.js involves defining routes, handling HTTP methods, and structuring the API in a way that adheres to RESTful principles. Here’s a step-by-step guide on how to create a basic RESTful API with Express.js:

1. Set Up Your Express App:

Ensure you have an Express.js application set up. If you haven’t, you can use the Express Application Generator or manually set up a basic Express app.

2. Define Routes for Resources:

Identify the resources your API will expose and define routes for them. For example, if you are building an API for managing tasks, you might have routes like /tasks to get all tasks and /tasks/:taskId to get a specific task.

// tasksRoutes.js
const express = require(‘express’);
const router = express.Router();

// Get all tasks
router.get(‘/tasks’, (req, res) => {
// Logic to fetch all tasks from the database
res.json({ message: ‘Get all tasks’ });
});

// Get a specific task by ID
router.get(‘/tasks/:taskId’, (req, res) => {
const taskId = req.params.taskId;
// Logic to fetch task by ID from the database
res.json({ message: `Get task with ID: ${taskId}` });
});

// Other routes for creating, updating, and deleting tasks can be added here

module.exports = router;

3. Use Routers in Your Main Application:

In your main application file (e.g., app.js or server.js), use the router by requiring and mounting it.

const express = require(‘express’);
const tasksRoutes = require(‘./tasksRoutes’); // Import your router

const app = express();
const port = 3000;

// Mount the tasksRoutes at /api
app.use(‘/api’, tasksRoutes);

// Your other routes and configurations go here

app.listen(port, () => {
console.log(`Server is running on http://localhost:${port}`);
});

4. Test Your API Endpoints:

Start your Express app and use tools like curl, Postman, or a browser to test your API endpoints. For example:

Get all tasks: GET http://localhost:3000/api/tasks
Get a specific task: GET http://localhost:3000/api/tasks/123

5. Implement CRUD Operations:

Extend your API by implementing CRUD (Create, Read, Update, Delete) operations for your resources. Add routes for creating, updating, and deleting tasks in the tasksRoutes.js file.

// tasksRoutes.js
// …

// Create a new task
router.post(‘/tasks’, (req, res) => {
// Logic to create a new task in the database
res.json({ message: ‘Create a new task’ });
});

// Update a task by ID
router.put(‘/tasks/:taskId’, (req, res) => {
const taskId = req.params.taskId;
// Logic to update task by ID in the database
res.json({ message: `Update task with ID: ${taskId}` });
});

// Delete a task by ID
router.delete(‘/tasks/:taskId’, (req, res) => {
const taskId = req.params.taskId;
// Logic to delete task by ID from the database
res.json({ message: `Delete task with ID: ${taskId}` });
});

module.exports = router;

6. Handle Request and Response:

Inside each route handler, handle the request and response appropriately. You can use an ORM like Mongoose (for MongoDB), Sequelize (for SQL databases), or any other database library to interact with your database.

// tasksRoutes.js
const Task = require(‘./models/task’); // Assuming you have a Task model

router.get(‘/tasks’, async (req, res) => {
try {
const tasks = await Task.find();
res.json(tasks);
} catch (error) {
res.status(500).json({ message: error.message });
}
});

router.post(‘/tasks’, async (req, res) => {
const task = new Task({
title: req.body.title,
description: req.body.description,
// Additional fields based on your Task model
});

try {
const newTask = await task.save();
res.status(201).json(newTask);
} catch (error) {
res.status(400).json({ message: error.message });
}
});

// Implement similar handling for other CRUD operations

7. Use Middleware for Request Validation:

You may want to use middleware to validate and sanitize the incoming request data.

// tasksRoutes.js
router.post(‘/tasks’, validateTask, async (req, res) => {
// Handle the request
});

function validateTask(req, res, next) {
// Validate req.body and handle errors
// Call next() if validation passes
}

8. Add Authentication and Authorization:

For secure APIs, consider adding authentication and authorization middleware.

// tasksRoutes.js
const passport = require(‘passport’);

router.get(‘/tasks’, passport.authenticate(‘jwt’, { session: false }), (req, res) => {
// Handle the authenticated request
});

9. Handle Errors:

Implement error handling middleware to catch and respond to errors.

// tasksRoutes.js
router.use((err, req, res, next) => {
console.error(err.stack);
res.status(500).json({ message: 'Internal Server Error' });
});

10. Documentation:

Consider adding API documentation using tools like Swagger or documenting your API routes in your project’s README file.

Building a RESTful API with Express involves defining routes, handling HTTP methods, interacting with a database, and implementing middleware for validation, authentication, and error handling. Customize the code according to your specific requirements and database technology used.

9. Middleware for Security:

Middleware plays a crucial role in enhancing the security of your Express.js application. By incorporating security middleware, you can protect your application against common web security vulnerabilities. Here are some security-related middleware you can use in an Express.js application:

1. Helmet:

Helmet is a collection of middleware functions that help secure Express applications by setting various HTTP headers.

npm install helmet

In your Express application:

const express = require(‘express’);
const cors = require(‘cors’);

const app = express();
const port = 3000;

// Use CORS middleware
app.use(cors());

// Your routes and other configurations go here

app.listen(port, () => {
console.log(`Server is running on http://localhost:${port}`);
});

Helmet adds security headers such as X-Content-Type-Options, X-Frame-Options, Strict-Transport-Security, and more.

2. CORS Middleware:

If your application serves APIs that may be accessed by other domains, consider using CORS middleware to control access to your resources.

npm install cors

In your Express application:

const express = require(‘express’);
const cors = require(‘cors’);

const app = express();
const port = 3000;

// Use CORS middleware
app.use(cors());

// Your routes and other configurations go here

app.listen(port, () => {
console.log(`Server is running on http://localhost:${port}`);
});

3. Express Rate Limit:

Express Rate Limit middleware can help protect against brute force attacks and limit the rate at which clients can make requests.

npm install express-rate-limit

In your Express application:

const express = require(‘express’);
const rateLimit = require(‘express-rate-limit’);

const app = express();
const port = 3000;

// Use rate limiting middleware
const limiter = rateLimit({
windowMs: 15 * 60 * 1000, // 15 minutes
max: 100, // limit each IP to 100 requests per windowMs
});

app.use(limiter);

// Your routes and other configurations go here

app.listen(port, () => {
console.log(`Server is running on http://localhost:${port}`);
});

4. Helmet Content Security Policy (CSP):

Content Security Policy (CSP) helps prevent various types of attacks, such as cross-site scripting (XSS). The helmet-csp module provides a middleware for setting CSP headers.

npm install helmet-csp

In your Express application:

const express = require(‘express’);
const helmet = require(‘helmet’);
const csp = require(‘helmet-csp’);

const app = express();
const port = 3000;

// Use Helmet and CSP middleware
app.use(helmet());
app.use(csp({
directives: {
defaultSrc: [“‘self'”],
scriptSrc: [“‘self'”, ‘example.com’],
styleSrc: [“‘self'”, ‘maxcdn.bootstrapcdn.com’],
},
}));

// Your routes and other configurations go here

app.listen(port, () => {
console.log(`Server is running on http://localhost:${port}`);
});

5. Express Validator:

Express Validator is middleware for Express.js that provides validation and sanitization of user input.

npm install express-validator

In your Express application:

const express = require(‘express’);
const { body, validationResult } = require(‘express-validator’);

const app = express();
const port = 3000;

// Example route with input validation
app.post(‘/signup’, [
body(‘username’).isLength({ min: 5 }).withMessage(‘Username must be at least 5 characters’),
body(’email’).isEmail().withMessage(‘Invalid email’),
body(‘password’).isStrongPassword().withMessage(‘Password is not strong enough’),
], (req, res) => {
const errors = validationResult(req);
if (!errors.isEmpty()) {
return res.status(400).json({ errors: errors.array() });
}

// Process the signup logic
res.json({ message: ‘Signup successful’ });
});

// Your other routes and configurations go here

app.listen(port, () => {
console.log(`Server is running on http://localhost:${port}`);
});

These are just a few examples of security-related middleware for an Express.js application. Depending on your application’s specific needs and vulnerabilities, you may need to implement additional security measures. Always stay updated on security best practices and regularly audit your application for potential vulnerabilities.

10. Testing Express Applications:

Testing is a critical aspect of software development to ensure the reliability and correctness of your application. In the context of an Express.js application, testing typically involves unit testing, integration testing, and end-to-end testing. Below are some common tools and approaches for testing Express.js applications:

1. Mocha:

Mocha is a popular testing framework for JavaScript, and it is often used for testing Express.js applications. It provides a clean and flexible structure for organizing tests.

Install Mocha:

npm install mocha --save-dev

Create a test file, for example, test/app.test.js, and run the tests:

npx mocha test/app.test.js

2. Chai:

Chai is a BDD/TDD assertion library that can be paired with Mocha for expressive and readable tests.

Install Chai:

npm install chai --save-dev

Example usage in a Mocha test file:

const chai = require(‘chai’);
const chaiHttp = require(‘chai-http’);
const app = require(‘../app’); // Import your Express app

chai.use(chaiHttp);
const { expect } = chai;

describe(‘GET /’, () => {
it(‘should return “Hello, World!”‘, async () => {
const res = await chai.request(app).get(‘/’);
expect(res).to.have.status(200);
expect(res.text).to.equal(‘Hello, World!’);
});
});

3. Supertest:

Supertest is a library specifically designed for testing HTTP assertions. It can be used with Mocha and Chai for testing Express.js applications.

Install Supertest:

npm install supertest --save-dev

Example usage in a Mocha test file:

const request = require(‘supertest’);
const app = require(‘../app’); // Import your Express app

describe(‘GET /’, () => {
it(‘should return “Hello, World!”‘, async () => {
const res = await request(app).get(‘/’);
expect(res.statusCode).to.equal(200);
expect(res.text).to.equal(‘Hello, World!’);
});
});

4. Sinon:

Sinon is a library for creating spies, stubs, and mocks in JavaScript. It’s useful for testing functions and making assertions about their behavior.

Install Sinon:

npm install sinon --save-dev

Example usage in a Mocha test file:

const sinon = require(‘sinon’);
const myFunction = require(‘../myFunction’); // Import the function you want to test

describe(‘myFunction’, () => {
it(‘should call the callback’, () => {
const callback = sinon.spy();
myFunction(callback);
sinon.assert.calledOnce(callback);
});
});

5. Testing Database Interactions:

When testing Express applications that interact with databases, consider using an in-memory database or a dedicated testing database to avoid altering the production data. Tools like Mongoose for MongoDB or Sequelize for SQL databases provide features to facilitate testing.

6. Integration and End-to-End Testing:

For integration and end-to-end testing, tools like Cypress or Puppeteer can be used. These tools simulate user interactions and provide a higher level of testing, covering multiple components of your application.

7. Continuous Integration (CI):

Integrate your testing process into your CI/CD pipeline. Popular CI services like Travis CI, CircleCI, or GitHub Actions can be configured to run your tests automatically on each code push.

Remember to tailor your testing strategy based on your application’s specific requirements and complexity. A good test suite provides confidence in the stability and correctness of your Express.js application.

1. Introduction to Express.js:

Hello World Example:

2. Setting Up Express.js:

1. Create a Project Directory:

2. Initialize the Project:

3. Install Express.js:

4. Create a Server File:

5. Run Your Express App:

Additional Steps (Optional):

3. Routing in Express:

4. Middleware in Express:

Built-in Middleware:

Custom Middleware:

Error Handling Middleware:

Route-Specific Middleware:

Third-Party Middleware:

5. Express Application Generator:

1. Install Express Generator Globally:

2. Generate an Express App:

3. Navigate to the Project Directory:

4. Install Dependencies:

5. Start the Express App:

Project Structure:

Customizing Templates:

6. Handling Forms and Parsing Data:

1. Set Up Your Express App:

2. Create an HTML Form:

3. Install Necessary Dependencies:

4. Configure Express to Use body-parser:

5. Handle Form Submission:

6. Test Your Form:

7. Express Routers:

1. Create a New Router File:

2. Use the Router in Your Main Application:

3. Test Your Routes:

4. Additional Router Features:

5. Sub-Routers:

8. RESTful APIs with Express:

1. Set Up Your Express App:

2. Define Routes for Resources:

3. Use Routers in Your Main Application:

4. Test Your API Endpoints:

5. Implement CRUD Operations:

6. Handle Request and Response:

7. Use Middleware for Request Validation:

8. Add Authentication and Authorization:

9. Handle Errors:

10. Documentation:

9. Middleware for Security:

1. Helmet:

2. CORS Middleware:

3. Express Rate Limit:

4. Helmet Content Security Policy (CSP):

5. Express Validator:

10. Testing Express Applications:

1. Mocha:

2. Chai:

3. Supertest:

4. Sinon:

5. Testing Database Interactions:

6. Integration and End-to-End Testing:

7. Continuous Integration (CI):

Chandigarh

Mohali

Hamirpur

4. Configure Express to Use `body-parser`: