A Beginner-Friendly Guide to Building Your First API Using Node.js

Source: Dev.to

Introduction

If you’re new to backend development, building an API can feel intimidating.
Good news — with Node.js and Express you can create a functional API in just a few minutes.

What Is an API?

An API (Application Programming Interface) allows different applications to communicate with each other.

Example

• Frontend: “Give me all users.”
• Backend API: “Here you go!”

Setting Up the Project

mkdir my-first-api
cd my-first-api
npm init -y
npm install express

Creating the Server

Create a file named server.js and add the following code:

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

app.use(express.json());

// Home route
app.get('/', (req, res) => {
  res.send({ message: 'Welcome to your first Node.js API!' });
});

// Sample GET route
app.get('/api/users', (req, res) => {
  res.send([
    { id: 1, name: 'John' },
    { id: 2, name: 'Sarah' }
  ]);
});

// In‑memory users array
let users = [
  { id: 1, name: 'John' },
  { id: 2, name: 'Sarah' }
];

// POST route to add a user
app.post('/api/users', (req, res) => {
  const newUser = {
    id: users.length + 1,
    name: req.body.name
  };

  users.push(newUser);
  res.status(201).send(newUser);
});

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

Run the server:

node server.js

You should see:

Server running on http://localhost:3000

Running the API

Open your browser or use a tool like curl or Postman to interact with the endpoints.

• Home: http://localhost:3000
• Get users: http://localhost:3000/api/users

Using curl

curl http://localhost:3000/api/users

Using Postman (POST)

{
  "name": "Emily"
}

Send the request to http://localhost:3000/api/users to add a new user.

Next Steps

• Routing best practices – organize routes in separate modules.
• Environment variables – store configuration (e.g., port, DB credentials) with dotenv.
• Database integration – connect to MongoDB, PostgreSQL, etc., instead of using an in‑memory array.
• Authentication – implement JWT or session‑based auth for protected routes.
• Deployment – deploy to platforms like Heroku, Vercel, or Render.

You’re off to a great start — keep going! 🚀