Express.js Guide

Express.jsFast Web Framework

Learn Express.js routing, middleware, error handling, database integration, and building RESTful APIs.

Contents

Express.js Basics

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

javascript
// Installation
npm install express

// Basic Server
const express = require('express');
const app = express();
const PORT = 3000;

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

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

// Request and Response Objects
app.get('/user/:id', (req, res) => {
  // Request properties
  console.log(req.params); // Route parameters
  console.log(req.query);  // Query string
  console.log(req.body);   // Request body (needs middleware)
  console.log(req.headers); // Request headers
  
  // Response methods
  res.send('Hello');
  res.json({ message: 'Hello' });
  res.status(404).send('Not Found');
  res.redirect('/');
  res.render('view', { data });
});

// Different HTTP Methods
app.get('/users', (req, res) => {
  res.json({ users: [] });
});

app.post('/users', (req, res) => {
  res.status(201).json({ message: 'User created' });
});

app.put('/users/:id', (req, res) => {
  res.json({ message: 'User updated' });
});

app.delete('/users/:id', (req, res) => {
  res.json({ message: 'User deleted' });
});

app.patch('/users/:id', (req, res) => {
  res.json({ message: 'User partially updated' });
};