Hey, you’re back! 🙌 Chapter 1 was all about what Node.js is—now it’s time to build something real. By the end of this, you’ll have a working REST API that serves data, handles requests, and makes you feel like a coding wizard. No magic wand required—just JavaScript.

Let’s get this bread.

Express.js: Your API’s New BFF

Node.js is powerful, but writing a server from scratch? That’s like building a car to drive to the grocery store. Express.js is the Tesla of backend frameworks—minimal setup, maximum speed.

Why Express?

  • Simplifies routing (mapping URLs to code).
  • Adds middleware (think: plugins for your server).
  • Used by Netflix, Uber, and X(Twitter) (no big deal).

REST APIs in 60 Seconds ⏳

A REST API lets apps talk to each other over HTTP. Imagine your React app asking your Node.js server: “Hey, can I get some data?” and the server replying “Sure, here’s a JSON file!”

Key concepts:

  • Endpoints: URLs like /api/users or /api/posts.
  • HTTP Methods: GET (read), POST (create), PUT (update), DELETE (…you get it).
  • CRUD: Create, Read, Update, Delete (the four commandments of APIs).

Let’s Build a To-Do API (Because Why Not?)

We’re building a simple API to track tasks. Even Zuckerberg started with “Hello, World.”

Step 1: Set Up the Project

  1. Create a folder and initialize npm: 
mkdir todo-api && cd todo-api  
   npm init -y  # -y = "Yes to everything, I’m lazy"
  1. Install Express: 
npm install express

Step 2: The Bare Minimum Server

Create server.js:

// server.js  
const express = require('express');  
const app = express();  

// Let Express parse JSON (so you can send data in POST requests)  
app.use(express.json());  

// Basic route  
app.get('/', (req, res) => {  
  res.send('Your API is alive! 🎉');  
});  

// Start the server  
const PORT = 3000;  
app.listen(PORT, () => {  
  console.log(`Server dancing on http://localhost:${PORT}`);  
});

Run it:

node server.js

Visit http://localhost:3000 in your browser. If you see the message, you’ve just built a server.

Adding CRUD Endpoints

Let’s fake a database (for now) using an array.

// Fake "database"  
let todos = [  
  { id: 1, task: "Learn Node.js", done: false },  
  { id: 2, task: "Build an API", done: true }  
];  

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

// POST a new todo  
app.post('/api/todos', (req, res) => {  
  const newTodo = {  
    id: todos.length + 1,  
    task: req.body.task,  
    done: false  
  };  
  todos.push(newTodo);  
  res.status(201).json(newTodo);  // 201 = "Created"  
});

Test it with Postman:

  1. Send a GET to http://localhost:3000/api/todos – you’ll see your fake todos.
  2. Send a POST with JSON body { "task": "Buy coffee" } – watch your array grow!

Middleware: The Secret Sauce

Middleware functions can:

  • Log requests.
  • Authenticate users.
  • Handle errors.

Example: Add a request logger

// Log every request  
app.use((req, res, next) => {  
  console.log(`[${new Date().toISOString()}] ${req.method} ${req.url}`);  
  next();  // Pass control to the next middleware  
});

Now your terminal will show:

[2025-06-15T10:30:00Z] GET /api/todos

Error Handling (Because Stuff Breaks)

Ever seen “Cannot GET /api/todo”? Let’s fix that.

// Handle 404s  
app.use((req, res) => {  
  res.status(404).json({ error: "Route not found. Did you mean /api/todos?" });  
});  

// Global error handler  
app.use((err, req, res, next) => {  
  console.error(err.stack);  
  res.status(500).json({ error: "Oops, our server had a ☕ moment." });  
});

Why This Matters

  • Foundational Skills: Every backend role expects REST API knowledge.
  • Full-Stack Power: Connect this API to your React/Vue frontend tomorrow.
  • Scalability: Later, swap the fake array with MongoDB/Postgres.

Level Up: 3 Pro Tips

  1. Use nodemon to auto-restart your server on changes: 
npm install -g nodemon  
   nodemon server.js
  1. Structure your code with folders like routes/ and controllers/.
  2. Always validate data (try the joi library).

Quiz Time! 🧠

Test your Express knowledge here:

👉 Express.JS Quiz

What’s Next?

In Chapter 3, we’ll connect this API to a real database (MongoDB) and deploy it to the cloud. Until then:

  1. Add PUT and DELETE endpoints.
  2. Experiment with Postman to test your routes.

About the Author

Still Abhinav, still caffeinated. I once spent 3 hours debugging an API only to realize I forgot a comma. Now I write guides so you don’t have to. Find more rants and memes at ExamShala.in.

P.S. Hit a wall? Screenshot your code and tag me on Twitter. Let’s fix it together! 💪