Building RESTful APIs with Node.js & Express

What to do:

1. Initialize project and install dependencies:
   bash

   npm init -y
   npm install express body-parser cors
   npm install --save-dev nodemon

2. Create basic server:
   javascript

   const express = require('express');
   const app = express();
   
   app.use(express.json());
   
   app.get('/', (req, res) => {
     res.json({ message: 'API is running' });
   });
   
   const PORT = process.env.PORT || 3000;
   app.listen(PORT, () => {
     console.log(`Server running on port ${PORT}`);
   });

Example:

Folder structure for scalability:

project/
├── src/
│   ├── controllers/
│   ├── routes/
│   ├── models/
│   ├── middleware/
│   └── app.js
├── .env
└── package.json

What to do:

1. Create modular routes:
   javascript

   // routes/users.js
   const express = require('express');
   const router = express.Router();
   const { getUsers, createUser } = require('../controllers/users');
   
   router.route('/')
     .get(getUsers)
     .post(createUser);
   
   module.exports = router;

2. Implement controller logic:
   javascript

   // controllers/users.js
   const getUsers = async (req, res) => {
     try {
       const users = await User.find({});
       res.status(200).json(users);
     } catch (error) {
       res.status(500).json({ message: error.message });
     }
   };

Example:

Registering routes in main app:

// app.js
const userRoutes = require('./routes/users');
app.use('/api/users', userRoutes);

What to do:

1. Implement error middleware:
   javascript

   // middleware/errorHandler.js
   const errorHandler = (err, req, res, next) => {
     const statusCode = err.statusCode || 500;
     res.status(statusCode).json({
       message: err.message,
       stack: process.env.NODE_ENV === 'production' ? '🥞' : err.stack
     });
   };

2. Add security middleware:
   javascript

   app.use(helmet()); // Sets various HTTP headers
   app.use(cors({
     origin: process.env.CLIENT_URL
   }));
   app.use(rateLimit({
     windowMs: 15 * 60 * 1000, // 15 minutes
     max: 100 // limit each IP to 100 requests per window
   }));

Example:

Custom error class for consistent errors:

class ErrorResponse extends Error {
  constructor(message, statusCode) {
    super(message);
    this.statusCode = statusCode;
  }
}

// Usage in controller
throw new ErrorResponse('User not found', 404);