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Express.js is one of the most popular frameworks for Node.js, enabling developers to build scalable and efficient backend systems. Whether you’re creating RESTful APIs or full-stack applications, Express.js simplifies the process with its minimalistic and flexible design.
You Should Know:
1. Setting Up Express.js
To get started with Express.js, you need to install Node.js and npm. Once installed, create a new project and install Express:
mkdir my-express-app cd my-express-app npm init -y npm install express
Create an `index.js` file and set up a basic server:
[javascript]
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}`);
});
[/javascript]
Run the server using:
node index.js
2. Routing in Express.js
Express.js makes routing simple. Here’s an example of handling different HTTP methods:
[javascript]
app.get(‘/api/users’, (req, res) => {
res.json({ message: ‘Fetch all users’ });
});
app.post(‘/api/users’, (req, res) => {
res.json({ message: ‘Create a new user’ });
});
app.put(‘/api/users/:id’, (req, res) => {
res.json({ message: `Update user with ID ${req.params.id}` });
});
app.delete(‘/api/users/:id’, (req, res) => {
res.json({ message: `Delete user with ID ${req.params.id}` });
});
[/javascript]
3. Middleware in Express.js
Middleware functions are used to process requests before they reach the final route handler. For example, logging middleware:
[javascript]
app.use((req, res, next) => {
console.log(${req.method} ${req.url});
next();
});
[/javascript]
You can also use built-in middleware like `express.json()` for parsing JSON payloads:
[javascript]
app.use(express.json());
[/javascript]
4. Error Handling
Centralized error handling ensures better debugging. Use `express-async-handler` for async routes:
npm install express-async-handler
Example:
[javascript]
const asyncHandler = require(‘express-async-handler’);
app.get(‘/api/data’, asyncHandler(async (req, res) => {
const data = await fetchData();
if (!data) throw new Error(‘Data not found’);
res.json(data);
}));
app.use((err, req, res, next) => {
res.status(500).json({ error: err.message });
});
[/javascript]
5. Database Integration
Express.js works seamlessly with databases like MongoDB. Install Mongoose for MongoDB integration:
npm install mongoose
Example:
[javascript]
const mongoose = require(‘mongoose’);
mongoose.connect(‘mongodb://localhost:27017/mydb’, { useNewUrlParser: true, useUnifiedTopology: true });
const UserSchema = new mongoose.Schema({
name: String,
email: String,
});
const User = mongoose.model(‘User’, UserSchema);
app.post(‘/api/users’, async (req, res) => {
const user = new User(req.body);
await user.save();
res.json(user);
});
[/javascript]
What Undercode Say:
Express.js is a powerful tool for building scalable APIs, but mastering it requires practice. Here are some additional Linux and Windows commands to enhance your development workflow:
- Linux Commands:
– `curl http://localhost:3000/api/users` – Test your API endpoints.
– `sudo systemctl restart nginx` – Restart Nginx server after deploying your app.
– `netstat -tuln` – Check open ports on your server. -
Windows Commands:
– `tasklist | findstr node` – Find Node.js processes running on your system.
– `ipconfig` – Check your network configuration.
– `npm install -g nodemon` – Install nodemon for automatic server restarts.
Express.js is a must-learn for backend developers, and integrating it with databases, middleware, and proper error handling will make your applications robust and scalable.
Expected Output:
- A fully functional Express.js server with routing, middleware, and error handling.
- Integration with MongoDB using Mongoose.
- Enhanced debugging and testing using Linux and Windows commands.
For further reading, visit the official Express.js documentation.
References:
Reported By: Sumit Yadav – Hackers Feeds
Extra Hub: Undercode MoN
Basic Verification: Pass ✅
