How to Create a REST API with Node.js and Express

Creating a REST API is one of the most common tasks developers perform when building web applications. In this tutorial, we’ll guide you through setting up a RESTful API using Node.js and the Express framework. Express is a minimal and flexible Node.js web application framework that makes it easier to build APIs quickly.

Let’s dive into the process.

Prerequisites

Before we start, ensure you have the following installed:

Node.js: You can download and install Node.js from here.
npm (Node Package Manager): npm comes with Node.js, so installing Node will also install npm.
A code editor like VS Code.
Basic knowledge of JavaScript and Node.js.

Step 1: Initialize a Node.js Project

Start by creating a directory for your project and initialize a new Node.js project:

Open your terminal or command prompt.
Create a new directory and navigate to it:bashCopy codemkdir my-api cd my-api
Initialize a new Node.js project:bashCopy codenpm init -y This will create a package.json file with default values.

Step 2: Install Dependencies

Next, install Express and nodemon (for automatic server restarts during development):

bashCopy codenpm install express
npm install --save-dev nodemon

Express is the web framework for Node.js.
Nodemon is a development tool that monitors for changes in the source code and automatically restarts the server.

Add the following script in your package.json file to use nodemon to start your server:

jsonCopy code"scripts": {
  "start": "nodemon server.js"
}

Step 3: Create the API Server

Now, let’s create the server file (server.js):

In your project folder, create a file called server.js:

bashCopy codetouch server.js

Open server.js and add the following code to set up the Express server:

javascriptCopy code// server.js
const express = require('express');
const app = express();
const port = 3000;

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

// Sample data (in-memory storage for demonstration purposes)
let users = [
  { id: 1, name: 'John Doe', email: 'john@example.com' },
  { id: 2, name: 'Jane Smith', email: 'jane@example.com' },
];

// Root endpoint to check if the API is working
app.get('/', (req, res) => {
  res.send('Welcome to the Node.js REST API!');
});

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

// GET a user by ID
app.get('/api/users/:id', (req, res) => {
  const userId = parseInt(req.params.id);
  const user = users.find((u) => u.id === userId);

  if (!user) {
    return res.status(404).send('User not found');
  }

  res.json(user);
});

// POST a new user
app.post('/api/users', (req, res) => {
  const { name, email } = req.body;

  if (!name || !email) {
    return res.status(400).send('Name and email are required');
  }

  const newUser = {
    id: users.length + 1,
    name,
    email,
  };

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

// PUT to update a user's details
app.put('/api/users/:id', (req, res) => {
  const userId = parseInt(req.params.id);
  const { name, email } = req.body;

  const user = users.find((u) => u.id === userId);

  if (!user) {
    return res.status(404).send('User not found');
  }

  user.name = name || user.name;
  user.email = email || user.email;

  res.json(user);
});

// DELETE a user by ID
app.delete('/api/users/:id', (req, res) => {
  const userId = parseInt(req.params.id);
  const userIndex = users.findIndex((u) => u.id === userId);

  if (userIndex === -1) {
    return res.status(404).send('User not found');
  }

  users.splice(userIndex, 1);
  res.status(204).send();
});

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

Explanation of the Code:

Express Setup: We import Express, create an app instance, and set the port to 3000.
Middleware: The express.json() middleware is used to parse incoming JSON data.
Routes:
- GET /api/users: Returns a list of all users.
- GET /api/users/:id: Retrieves a user by ID.
- POST /api/users: Creates a new user and adds it to the users array.
- PUT /api/users/:id: Updates the user’s name and/or email.
- DELETE /api/users/:id: Deletes a user from the users array.

Step 4: Run the Server

Now that the server is set up, you can run it with the following command:

bashCopy codenpm start

This will start the server using nodemon, and it will be accessible at http://localhost:3000.

Step 5: Test the API Endpoints

You can test the API endpoints using tools like Postman, Insomnia, or even curl commands:

GET all users:
URL: http://localhost:3000/api/users
GET a user by ID:
URL: http://localhost:3000/api/users/1
POST a new user (Send JSON data in the request body):
URL: http://localhost:3000/api/users
Body:jsonCopy code{ "name": "Alice Johnson", "email": "alice@example.com" }
PUT (Update user details):
URL: http://localhost:3000/api/users/2
Body:jsonCopy code{ "name": "Jane Doe", "email": "janedoe@example.com" }
DELETE a user by ID:
URL: http://localhost:3000/api/users/1

Step 6: Conclusion

You’ve just created a simple REST API with Node.js and Express! This API has basic CRUD operations to manage users, and it runs on port 3000.