Express.js Basics

Routing, middleware, request/response handling, and RESTful API design with Express.

Overview

Express.js is the most popular web framework for Node.js, providing a minimal and flexible approach to building web applications and APIs.

Key Concepts

• Routing — Define URL patterns and their handlers
• Middleware — Functions that execute during the request-response cycle
• Request Object — req.params, req.query, req.body
• Response Object — res.json(), res.status(), res.send()
• Router — Modular route handlers for organizing code

Code Examples

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

app.use(express.json());

app.get('/api/users', (req, res) => {
  res.json([{ id: 1, name: 'Alice' }, { id: 2, name: 'Bob' }]);
});

app.post('/api/users', (req, res) => {
  const { name } = req.body;
  res.status(201).json({ id: 3, name });
});

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

Practice

Build a RESTful API with Express that supports CRUD operations for a resource.