Working with RESTful APIs

A RESTful API (Representational State Transfer API) is a way to allow clients (like web or mobile apps) to interact with a server using HTTP methods.
Express.js is widely used to create RESTful APIs because it simplifies routing, middleware, and JSON handling.

1. RESTful API Basics

2. Setting Up Express for REST API

const express = require('express');
const app = express();
const port = 3000;

// Middleware to parse JSON bodies
app.use(express.json());

// Dummy data
let users = [
  { id: 1, name: 'Alice' },
  { id: 2, name: 'Bob' }
];

3. Creating Routes

GET all users

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

GET user by ID

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

POST create a new user

app.post('/users', (req, res) => {
  const newUser = {
    id: users.length + 1,
    name: req.body.name
  };
  users.push(newUser);
  res.status(201).json(newUser);
});

PUT update a user

app.put('/users/:id', (req, res) => {
  const user = users.find(u => u.id === parseInt(req.params.id));
  if (!user) return res.status(404).json({ error: 'User not found' });
  
  user.name = req.body.name;
  res.json(user);
});

DELETE a user

app.delete('/users/:id', (req, res) => {
  const index = users.findIndex(u => u.id === parseInt(req.params.id));
  if (index === -1) return res.status(404).json({ error: 'User not found' });

  const deletedUser = users.splice(index, 1);
  res.json(deletedUser[0]);
});

4. Running the API

1. Start server:

node app.js

2. Use tools like Postman, Insomnia, or fetch/axios from a frontend to test endpoints.

5. Best Practices for RESTful APIs

• Use plural nouns for resources: /users, /posts

• Return proper HTTP status codes: 200, 201, 400, 404, 500

• Validate request data before saving/updating

• Separate routes into modular files using Express Router

• Handle errors consistently using error-handling middleware

6. Example Project Structure

express-api/
│
├─ routes/
│   └─ users.js
│
├─ app.js
└─ package.json

• app.js → Main server and middleware

• routes/users.js → All user-related routes

Express.js makes it easy to build RESTful APIs for both small and large applications. Once you combine this with middleware, authentication, and database integration, you can create full-featured backends.