Introduction to Express.js

What is Express.js?

Express.js is a minimal and flexible Node.js web application framework that provides a robust set of features for building web and mobile applications. It facilitates the rapid development of Node-based web applications by providing a set of tools and features.

Key Features:

• Lightweight and minimalistic
• Middleware support
• Easy routing
• Flexible and scalable
• Supports various template engines

Installation

To install Express.js, you need to have Node.js and npm installed. Follow the steps below:

1. Open your terminal.
2. Create a new directory for your project:

mkdir my-express-app

3. Navigate into your project directory:

cd my-express-app

4. Initialize a new npm project:

npm init -y

5. Install Express:

npm install express

Basic Usage

Once Express is installed, you can create a basic server with just a few lines of code:

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 on http://localhost:${PORT}`);
});

To run your server, execute the following command in your terminal:

node index.js

Routing

Routing refers to how an application responds to client requests for a particular endpoint. Express makes it easy to define routes:

app.get('/about', (req, res) => {
    res.send('About Page');
});

app.post('/submit', (req, res) => {
    res.send('Form Submitted');
});

Middleware

Middleware functions are functions that have access to the request object (req), the response object (res), and the next middleware function in the application’s request-response cycle. They are used for tasks such as logging, authentication, and more.

Example of a simple middleware:

app.use((req, res, next) => {
    console.log(`${req.method} request for '${req.url}'`);
    next();
});

FAQ