Express.js Basics

Express is a minimal and flexible Node.js web application framework that provides a robust set of features for web and mobile applications.

1. Setting Up Express

First, install it via npm:

npm install express

2. Basic Server

import express from 'express';
const app = express();

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

app.listen(3000, () => {
  console.log('Server running on port 3000');
});

3. Routing

Routing refers to how an application’s endpoints (URIs) respond to client requests.

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

app.post('/api/users', (req, res) => {
  res.send('User created!');
});

4. 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.

const logger = (req, res, next) => {
  console.log(`${req.method} ${req.url}`);
  next(); // Pass control to the next handler
};

app.use(logger); // Use middleware globally

[!TIP] Use express.json() middleware to parse JSON bodies from incoming requests.