Building a RESTful API with Node.js and Express

What is a REST API?

A RESTful API (Representational State Transfer Application Programming Interface) is an architectural style for designing networked applications. It relies on a stateless, client-server communication protocol, almost always HTTP. It's the most common way for web services to communicate.

Prerequisites

• Node.js installed on your machine.
• A basic understanding of JavaScript.

Step 1: Initialize Your Project

Create a new directory for your project and initialize it with npm.

mkdir my-api
cd my-api
npm init -y

Now, let's install Express, the most popular web framework for Node.js.

npm install express

Step 2: Set up the Express Server

Create a file named index.js and add the following code to create a basic server:

// index.js
const express = require('express');
const app = express();
const port = 3000;

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

app.listen(port, () => {
  console.log(`Server listening at http://localhost:${port}`);
});

Run your server with node index.js. You should see "Hello, World!" when you visit http://localhost:3000 in your browser.

Step 3: Define API Routes

Let's create a simple in-memory database and a few API endpoints to manage a list of users.

Update index.js:

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

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

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

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

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

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

app.listen(port, () => {
  console.log(`Server listening at http://localhost:${port}`);
});

You now have a basic REST API! You can test the new endpoints using tools like Postman or curl.

Conclusion

This is just the beginning. From here, you can connect to a real database, add authentication, validation, and much more to build a production-ready API.