How to Build a Simple REST API with Node.js and Express (2025 Guide)

Building a REST API is a key skill for developers in 2025. It doesn’t matter if you’re working on a web app, backend for mobile, or microservices – a well-designed API speeds up development and helps your project grow. This guide will show you how to create a basic REST API with Node.js and Express.js even if you’re just starting out.

🧰 Things You Need 

• Node.js on your computer (Get it here) 

• A grasp of JavaScript basics

• VS Code or another code editor 

• Postman or a similar tool to test APIs

📁 Step 1: Initialize Your Project

Open your terminal and run:

mkdir simple-rest-api
cd simple-rest-api
npm init -y

This creates a basic package.json file.

📦 Step 2: Install Express

• Install Express.js:
  
  npm install express

📄 Step 3: Create Your API Server

• Create a file called index.js and paste this code:

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

app.use(express.json());

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

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

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

// POST 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);
});

// DELETE a user
app.delete('/users/:id', (req, res) => {
  users = users.filter(u => u.id !== parseInt(req.params.id));
  res.send('User deleted');
});

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

🧪 Step 4: Test Your API

Use Postman or Hoppscotch to test these endpoints:

• DELETE /users/:id – Delete a user

• GET /users – List all users

• GET /users/:id – Get user by ID

• POST /users – Add new user (JSON body: { "name": "John" })

🔐 Step 5: Add CORS (Optional)

To allow cross-origin requests, install and enable CORS:

npm install cors

Then add to your code:

const cors = require('cors');
app.use(cors());

REST APIs are the backbone of nearly all modern web and mobile applications. Whether it’s a login system, dashboard, or mobile app, Node.js with Express is still one of the most popular ways to create high-performance REST APIs in 2025.

In this tutorial, you will learn how to create a simple REST API from scratch and learn how it works.

Why Use Node.js and Express for APIs?

Node.js + Express is popular because:

• Fast and lightweight

• JavaScript everywhere (frontend + backend)

• Huge ecosystem (npm)

• Easy to learn

• Great for real-time apps

Express simplifies routing, middleware, and request handling.

Step 1: Initialize a Node.js Project

Create a new folder and initialize your project.

mkdir simple-rest-api
cd simple-rest-api
npm init -y

Install Express:

npm install express

Optional but recommended (for auto-restart):

npm install nodemon --save-dev

Step 2: Create Basic Project Structure

simple-rest-api/
│
├── index.js
├── package.json
└── node_modules/

Step 3: Create Your Express Server

Create index.js and add:

const express = require("express");
const app = express();
const PORT = 3000;

// Middleware
app.use(express.json());

// Root route
app.get("/", (req, res) => {
  res.json({ message: "API is running 🚀" });
});

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

Run the server:

node index.js

Or using nodemon:

npx nodemon index.js

Step 4: Create Sample API Routes (CRUD)

We’ll create a simple in-memory users API.

Sample Data

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

---

🔹 GET – Fetch All Users

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

---

🔹 GET – Fetch 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 { name } = req.body;

  if (!name) {
    return res.status(400).json({ error: "Name is required" });
  }

  const newUser = {
    id: users.length + 1,
    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 || user.name;
  res.json(user);
});

---

🔹 DELETE – Remove a User

app.delete("/users/:id", (req, res) => {
  users = users.filter(u => u.id !== parseInt(req.params.id));
  res.json({ message: "User deleted successfully" });
});

---

🧪 Step 5: Test Your API

Use:

• Postman
• Thunder Client
• curl

Example Test

GET http://localhost:3000/users

Step 6: Add Basic Error Handling Middleware

app.use((err, req, res, next) => {
  console.error(err.stack);
  res.status(500).json({ error: "Something went wrong" });
});

Step 7: Security Best Practices (2025)

Even simple APIs should follow security basics.

✅ Essential Security Tips

Validate request data

Never trust client input

Use HTTPS in production

Hide environment variables

Add rate limiting

Enable CORS carefully

Optional packages:

npm install cors helmet express-rate-limit

Step 8: Organize Code (Recommended)

As your API grows, split files:

├── routes/
│   └── users.js
├── controllers/
├── middleware/
├── index.js

This improves maintainability and scalability.

Step 9: Prepare for Database Integration

In real projects, you’ll replace in-memory data with:

• MongoDB (Mongoose)
• PostgreSQL
• MySQL

Your API logic remains mostly the same.

---

🚀 Step 10: Deploy Your REST API

Free & popular platforms:

• Render
• Railway
• Fly.io
• Vercel (serverless)

Set environment variables properly before deployment.

Frequently Asked Questions
Is Express still relevant in 2025?

Yes. Express remains lightweight, stable, and widely used.

Should I use TypeScript?

Highly recommended for production APIs.

Is Node.js good for large apps?

Yes, with proper architecture and scaling.

Congratulations! You have just developed your first working REST API using Node.js and Express. It is a basic version, but it is a scalable structure – you can add middleware, authentication, and a database! Please check back for our next guide on connecting to MongoDB.More Posts on Flymingotech.in