Express Router and Route Parameters

// routes/products.js — a dedicated router file
const express = require('express');
const router  = express.Router();

const products = [
    { id: 1, name: 'Laptop',  price: 999 },
    { id: 2, name: 'Monitor', price: 399 },
];

// GET /products  (with optional ?category= query)
router.get('/', (req, res) => {
    const { category, sort } = req.query;
    let result = products;
    if (category) result = result.filter(p => p.category === category);
    if (sort === 'price') result = result.sort((a, b) => a.price - b.price);
    res.json(result);
});

// GET /products/:id
router.get('/:id', (req, res) => {
    const product = products.find(p => p.id === parseInt(req.params.id));
    if (!product) return res.status(404).json({ error: 'Not found' });
    res.json(product);
});

// GET /products/:id/reviews
router.get('/:id/reviews', (req, res) => {
    res.json({ productId: req.params.id, reviews: [] });
});

module.exports = router;

// app.js — mount the router:
// const productRouter = require('./routes/products');
// app.use('/products', productRouter);
// Now: GET /products, GET /products/1, GET /products/1/reviews