Introduction
If you are new to backend development and want to build powerful web applications, Express.js is an excellent place to start. Express.js is a fast, minimalist framework for Node.js that helps developers create web applications easily.
In this guide, we will explore what Express.js is, its features, installation process, and how to build a simple web server using Express.js.
What is Express.js?
Express.js is a popular backend framework for Node.js that simplifies web application development. It provides essential tools and features to handle routes, middleware, and HTTP requests efficiently.
Why Use Express.js?
- Easy to Learn – Simple and beginner-friendly.
- Lightweight – Minimalist and efficient.
- Fast – Built on Node.js for high performance.
- Flexible – Can be used for APIs, web applications, and more.
- Large Community – Many resources and support available.
Installing Express.js
Before installing Express.js, ensure you have Node.js and npm installed on your system.
Step 1: Install Node.js
Download and install Node.js from the official website: https://nodejs.org/
Step 2: Create a New Project
Open your terminal or command prompt and run the following commands:
mkdir my-express-app
cd my-express-app
npm init -y
This creates a new project directory and initializes a package.json file.
Step 3: Install Express.js
Run the following command to install Express.js:
npm install express
This will download and add Express.js to your project.
Creating a Simple Express.js Server
Now, let’s build a simple web server using Express.js.
Step 1: Create an index.js File
Inside your project folder, create a file named index.js and open it in a code editor.
Step 2: Write Express.js Code
Add the following code to index.js:
const express = require('express');
const app = express();
const port = 3000;
// Define a route
app.get('/', (req, res) => {
res.send('Hello, World! Welcome to Express.js!');
});
// Start the server
app.listen(port, () => {
console.log(`Server is running on http://localhost:${port}`);
});
Step 3: Run the Server
Save the file and run the following command in your terminal:
node index.js
Now, open your browser and go to http://localhost:3000/. You should see “Hello, World! Welcome to Express.js!” displayed.
Understanding Express.js Core Concepts
1. Routes
Routes define how an application responds to a client request. Example:
app.get('/about', (req, res) => {
res.send('About Page');
});
2. Middleware
Middleware functions process requests before they reach the final route handler. Example:
app.use((req, res, next) => {
console.log('Middleware executed');
next();
});
3. Handling POST Requests
To handle form data or API requests:
app.use(express.json());
app.post('/data', (req, res) => {
res.json({ message: 'Data received', data: req.body });
});
Building a Simple API with Express.js
Let’s create a simple API that returns user data.
Step 1: Define an API Route
const users = [
{ id: 1, name: 'John Doe' },
{ id: 2, name: 'Jane Doe' }
];
app.get('/api/users', (req, res) => {
res.json(users);
});
Step 2: Test the API
Run your server and visit http://localhost:3000/api/users in your browser or Postman to see the user data in JSON format.
Conclusion
Express.js makes backend development fast, simple, and scalable. With its minimal structure and powerful features, you can build APIs, web applications, and more with ease.
Next Steps:
- Learn more about Express.js Middleware.
- Explore Database Integration (MongoDB, MySQL).
- Build a complete RESTful API.
Now that you have a basic understanding of Express.js, start building your own projects and level up your backend development skills!
