Building REST API with Pure Node.js

Now that you know how to serve HTML and static files, let's take it a step further and build a real **REST API** using only Node.js built-in modules. This will give you a deep understanding of how APIs work before you start using frameworks like Express.

What is a REST API?

A REST API is a way for different software applications to communicate over HTTP. It uses standard HTTP methods (GET, POST, PUT, DELETE) to perform CRUD operations on resources.

HTTP Method	CRUD Operation	Example Endpoint
GET	Read	`/api/users` – get all users
GET	Read	`/api/users/1` – get user with id 1
POST	Create	`/api/users` – create a new user
PUT	Update	`/api/users/1` – update user with id 1
DELETE	Delete	`/api/users/1` – delete user with id 1

Think of a REST API as a restaurant menu. You look at the menu (GET), order food (POST), ask for a change (PUT), or cancel your order (DELETE).

Our Project: Simple User API

We'll build an API that manages a list of users. We'll store users in memory (an array) for simplicity. In a real application, you'd use a database.

Step 1: Setting Up the Server

const http = require('http');
const url = require('url');

let users = [
  { id: 1, name: 'John Doe', email: 'john@example.com' },
  { id: 2, name: 'Jane Smith', email: 'jane@example.com' }
];

const server = http.createServer((req, res) => {
  <!-- Set JSON as default content type -->
  res.setHeader('Content-Type', 'application/json');
  
  const parsedUrl = url.parse(req.url, true);
  const pathname = parsedUrl.pathname;
  const method = req.method;
  
  <!-- Handle routes -->
  <!-- We'll fill this in next steps -->
});

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

Step 2: GET All Users

if (pathname === '/api/users' && method === 'GET') {
  res.writeHead(200);
  res.end(JSON.stringify(users));
}

Step 3: GET Single User by ID

if (pathname.match(/^/api/users/d+$/) && method === 'GET') {
  const id = parseInt(pathname.split('/')[3]);
  const user = users.find(u => u.id === id);
  
  if (user) {
    res.writeHead(200);
    res.end(JSON.stringify(user));
  } else {
    res.writeHead(404);
    res.end(JSON.stringify({ error: 'User not found' }));
  }
}

Step 4: POST – Create New User

For POST requests, we need to read the request body. This is done by listening to `data` and `end` events.

if (pathname === '/api/users' && method === 'POST') {
  let body = '';
  
  req.on('data', chunk => {
    body += chunk.toString();
  });
  
  req.on('end', () => {
    try {
      const newUser = JSON.parse(body);
      
      <!-- Generate new ID -->
      const id = users.length ? Math.max(...users.map(u => u.id)) + 1 : 1;
      const user = { id, ...newUser };
      users.push(user);
      
      res.writeHead(201); <!-- Created -->
      res.end(JSON.stringify(user));
    } catch (err) {
      res.writeHead(400);
      res.end(JSON.stringify({ error: 'Invalid JSON' }));
    }
  });
}

Step 5: PUT – Update User

if (pathname.match(/^/api/users/d+$/) && method === 'PUT') {
  const id = parseInt(pathname.split('/')[3]);
  let body = '';
  
  req.on('data', chunk => {
    body += chunk.toString();
  });
  
  req.on('end', () => {
    try {
      const updatedData = JSON.parse(body);
      const index = users.findIndex(u => u.id === id);
      
      if (index !== -1) {
        users[index] = { ...users[index], ...updatedData };
        res.writeHead(200);
        res.end(JSON.stringify(users[index]));
      } else {
        res.writeHead(404);
        res.end(JSON.stringify({ error: 'User not found' }));
      }
    } catch (err) {
      res.writeHead(400);
      res.end(JSON.stringify({ error: 'Invalid JSON' }));
    }
  });
}

Step 6: DELETE – Remove User

if (pathname.match(/^/api/users/d+$/) && method === 'DELETE') {
  const id = parseInt(pathname.split('/')[3]);
  const index = users.findIndex(u => u.id === id);
  
  if (index !== -1) {
    users.splice(index, 1);
    res.writeHead(204); <!-- No content -->
    res.end();
  } else {
    res.writeHead(404);
    res.end(JSON.stringify({ error: 'User not found' }));
  }
}

Step 7: 404 for unknown routes

res.writeHead(404);
res.end(JSON.stringify({ error: 'Route not found' }));

Two Minute Drill

REST APIs use HTTP methods to perform CRUD operations.
Use `req.method` and `req.url` to route requests.
For POST/PUT, collect the request body by listening to `data` and `end` events.
Always parse JSON body with `JSON.parse()` and handle errors.
Send appropriate status codes (200, 201, 204, 400, 404).
This is how Express and other frameworks work under the hood.

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Building REST API with Pure Node.js

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