Step-by-Step Guide to Using Express.js

1. Install Node.js and Initialize a Project

First, ensure that Node.js is installed:

node -v

Create a new project:

mkdir express-app && cd express-app
npm init -y

2. Install Express.js

Run the following command to install Express.js:

npm install express

3. Create a Basic Express Server

Create a file server.js and add the following code:

const express = require('express');
const app = express();

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

const PORT = 3000;
app.listen(PORT, () => {
  console.log(`Server running at http://localhost:${PORT}/`);
});

Run the server:

node server.js

4. Handling Multiple Routes

Modify server.js to support multiple routes:

app.get('/', (req, res) => {
  res.send('<h1>Home Page</h1>');
});

app.get('/about', (req, res) => {
  res.send('<h1>About Us</h1>');
});

app.get('/api', (req, res) => {
  res.json({ message: 'Hello, API!' });
});

5. Using Middleware in Express

Middleware functions process requests before sending responses. Add express.json() middleware to handle JSON data:

app.use(express.json());

app.post('/data', (req, res) => {
  const receivedData = req.body;
  res.json({ message: 'Data received', data: receivedData });
});

6. Using Express Router for Modular Routing

To keep routes organized, create a routes.js file:

const express = require('express');
const router = express.Router();

router.get('/', (req, res) => {
  res.send('Welcome to the Home Route');
});

router.get('/users', (req, res) => {
  res.json([{ id: 1, name: 'John Doe' }]);
});

module.exports = router;

Import it in server.js:

const routes = require('./routes');
app.use('/', routes);

7. Handling Errors in Express

To catch errors globally, use error-handling middleware:

app.use((err, req, res, next) => {
  console.error(err.stack);
  res.status(500).send('Something broke!');
});

Conclusion

Express.js is a robust and flexible framework that makes Node.js web development simpler and faster. This guide covered:
✅ Setting up an Express.js server
✅ Handling routes and JSON responses
✅ Using middleware for request processing
✅ Implementing modular routing

For advanced features, explore authentication, database integration, and deployment. Need help with an Express API? 🚀