How do I create a simple REST API with Node.js and Express?

// Import the Express module
        const express = require('express');
        
        // Create an instance of an Express application
        const app = express();
        
        // Define a port for the server to listen on
        const PORT = 3000;
        
        // Middleware to parse JSON bodies
        app.use(express.json());
        
        // Define a simple GET route
        app.get('/api', (req, res) => {
            res.json({ message: 'Welcome to the API!' });
        });
        
        // Define a POST route
        app.post('/api/data', (req, res) => {
            const data = req.body;
            res.json({ receivedData: data });
        });
        
        // Start the server
        app.listen(PORT, () => {
            console.log(`Server is running on http://localhost:${PORT}`);
        });