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A Beginner’s Guide to Building a REST API with Node.js and Express

#node #api #express #beginners

APIs power most of the apps we use every day — from social media to weather apps. A REST API (Representational State Transfer) is one of the most common ways to let applications communicate with each other. In this guide, we’ll walk step-by-step through building a simple REST API using Node.js and Express.

  • What You’ll Learn
  • What a REST API is
  • How to set up Node.js and Express
  • How to create routes for CRUD operations (Create, Read, Update, Delete)
  • How to test your API

Step 1: Initialize Your Project

First, create a new project folder and initialize npm.

mkdir rest-api-demo
cd rest-api-demo
npm init -y
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Then install Express:

npm install express
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Step 2: Create the Server

Create a file called server.js and set up a basic Express server:

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

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

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

node server.js

You should see:
*Server running on http://localhost:3000
*

Step 3: Create Routes

For this example, let’s build a simple API for managing a list of books.

let books = [
  { id: 1, title: "Atomic Habits", author: "James Clear" },
  { id: 2, title: "The Pragmatic Programmer", author: "Andrew Hunt" }
];

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

// GET a book by ID
app.get('/books/:id', (req, res) => {
  const book = books.find(b => b.id === parseInt(req.params.id));
  book ? res.json(book) : res.status(404).json({ message: "Book not found" });
});

// POST (Add a new book)
app.post('/books', (req, res) => {
  const newBook = {
    id: books.length + 1,
    title: req.body.title,
    author: req.body.author
  };
  books.push(newBook);
  res.status(201).json(newBook);
});

// PUT (Update a book)
app.put('/books/:id', (req, res) => {
  const book = books.find(b => b.id === parseInt(req.params.id));
  if (!book) return res.status(404).json({ message: "Book not found" });

  book.title = req.body.title;
  book.author = req.body.author;
  res.json(book);
});

// DELETE a book
app.delete('/books/:id', (req, res) => {
  books = books.filter(b => b.id !== parseInt(req.params.id));
  res.json({ message: "Book deleted" });
});
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Step 4: Test the API

You can use tools like Postman or cURL to test your endpoints:

GET /books → Get all books

GET /books/1 → Get book with ID 1

POST /books with JSON body → Add a new book

PUT /books/1 with JSON body → Update book with ID 1

DELETE /books/1 → Delete book with ID 1
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Step 5: Wrap Up

You’ve just built your first REST API with Node.js and Express. From here, you can expand it by connecting to a database (like MongoDB or PostgreSQL), adding authentication, or deploying it online.

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