How to build a REST API with Express.js?

Building a REST API with Express.js

A REST API (Representational State Transfer) uses HTTP methods to perform CRUD operations on resources. Express.js makes this straightforward with its routing system.

HTTP Methods → CRUD

HTTP Method	CRUD	Description
GET	Read	Retrieve a resource
POST	Create	Create a new resource
PUT	Update (full)	Replace a resource
PATCH	Update (partial)	Modify a resource
DELETE	Delete	Remove a resource

Complete Users REST API

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

app.use(express.json()); // parse JSON request body

// In-memory store (use a database in production)
let users = [
  { id: 1, name: 'Alice', email: 'alice@example.com' },
  { id: 2, name: 'Bob',   email: 'bob@example.com' },
];
let nextId = 3;

// GET /users — list all users
app.get('/users', (req, res) => {
  res.json(users);
});

// GET /users/:id — get one user
app.get('/users/:id', (req, res) => {
  const user = users.find(u => u.id === Number(req.params.id));
  if (!user) return res.status(404).json({ error: 'User not found' });
  res.json(user);
});

// POST /users — create a user
app.post('/users', (req, res) => {
  const { name, email } = req.body;
  if (!name || !email) {
    return res.status(400).json({ error: 'name and email are required' });
  }
  const user = { id: nextId++, name, email };
  users.push(user);
  res.status(201).json(user);
});

// PUT /users/:id — replace a user
app.put('/users/:id', (req, res) => {
  const index = users.findIndex(u => u.id === Number(req.params.id));
  if (index === -1) return res.status(404).json({ error: 'User not found' });
  users[index] = { id: Number(req.params.id), ...req.body };
  res.json(users[index]);
});

// PATCH /users/:id — partially update a user
app.patch('/users/:id', (req, res) => {
  const user = users.find(u => u.id === Number(req.params.id));
  if (!user) return res.status(404).json({ error: 'User not found' });
  Object.assign(user, req.body);
  res.json(user);
});

// DELETE /users/:id — delete a user
app.delete('/users/:id', (req, res) => {
  const index = users.findIndex(u => u.id === Number(req.params.id));
  if (index === -1) return res.status(404).json({ error: 'User not found' });
  users.splice(index, 1);
  res.status(204).send();
});

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

Request Object Cheatsheet

req.params.id       // URL parameter: /users/:id
req.query.page      // Query string: /users?page=2
req.body.name       // Request body (JSON)
req.headers['authorization']  // Request headers
req.method          // 'GET', 'POST', etc.
req.path            // '/users/1'
req.ip              // Client IP address

Response Object Cheatsheet

res.json({ data })          // Send JSON (sets Content-Type)
res.send('text')            // Send text/HTML
res.status(201).json(data)  // Set status + send JSON
res.status(204).send()      // No content
res.redirect('/new-url')    // Redirect
res.set('X-Custom', 'val')  // Set header

REST API Best Practices

Use nouns for resources: /users, /products (not /getUsers)
Use HTTP methods for actions, not URL verbs
Return appropriate status codes (200, 201, 400, 401, 404, 500)
Version your API: /api/v1/users
Always return JSON with consistent structure
Use plural resource names: /users not /user

Consistent Response Format

// Success
res.json({ success: true, data: user });

// Error
res.status(400).json({ success: false, error: 'Validation failed' });

// Paginated list
res.json({
  success: true,
  data: users,
  pagination: { page: 1, limit: 10, total: 100 }
});

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How to build a REST API with Express.js?

#Building a REST API with Express.js

#HTTP Methods → CRUD

#Complete Users REST API

#Request Object Cheatsheet

#Response Object Cheatsheet

#REST API Best Practices

#Consistent Response Format