Learning Backend - Part 2: Building a REST API with Express.js

Learning Backend – Part 2: Building a REST API with Express.js

Prerequisites

You should have completed
Part 1: Setting Up Your Backend Environment
.
Basic knowledge of JavaScript and Node.js.

1. Installing Express.js

In your project directory, install Express using npm:
```
npm install express
```
Optionally, install nodemon as a development dependency for automatic server reload:
```
npm install --save-dev nodemon
```
About nodemon: Nodemon monitors your source code for changes and automatically restarts your server. It adds minimal overhead during development and should be installed as a dev dependency.

Then, update your package.json scripts to include:
```
"start": "node server.js",
"dev": "nodemon server.js"
```

2. Creating a Basic Express Server

Create a new file named server.js in your project directory (path: my-backend-project/server.js). Add the following content:

const express = require('express');
const app = express();
const port = process.env.PORT || 3000;

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

// A simple base route
app.get('/', (req, res) => {
  res.send('Hello from Express!');
});

// --- Additional API endpoints will be added here ---

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

Updated Folder Structure:

my-backend-project/
├── .env              (from Part 1)
├── index.js          (from Part 1)
├── node_modules/
├── package-lock.json
├── package.json
└── server.js         (new file)

Run your server using:
```
node server.js
```
Or, if using nodemon:
```
npx nodemon server.js
```

3. Building REST API Endpoints

Add new API endpoints in your server.js file after your base route and before the app.listen call.
For example, insert the following code immediately after your app.get('/', ...) block:

// GET endpoint for users
app.get('/users', (req, res) => {
  // Sample users data (replace with database query)
  const users = [
    { id: 1, name: 'Alice' },
    { id: 2, name: 'Bob' }
  ];
  res.json(users);
});

// POST endpoint to add a new user
app.post('/users', (req, res) => {
  const newUser = req.body; // In a real app, validate and save this data
  res.status(201).json({ message: 'User created successfully', user: newUser });
});

Ensure these endpoint definitions are placed before the app.listen block so that they are registered before the server starts listening for requests.

4. Testing Your API

Use a tool like Postman, Insomnia, or curl to test your endpoints. For example, with curl:

# Test GET endpoint:
curl http://localhost:3000/users

# Test POST endpoint:
curl -X POST -H "Content-Type: application/json" -d '{"id":3,"name":"Charlie"}' http://localhost:3000/users

5. Next Steps & Enhancements

Add global error-handling middleware to capture and log errors.
Integrate your API with the PostgreSQL database from Part 1 to perform real CRUD operations.
Implement authentication and authorization for your endpoints.
Write tests for your API using frameworks like Mocha, Chai, or Jest.

Join the Conversation

Share your experiences, challenges, and tips with other learners and developers:

What endpoints did you build?
What challenges did you encounter while creating your API?
Do you have recommendations for best practices?

Happy coding! 🚀

Learning Backend – Part 2: Building a REST API with Express.js