Express Router for Modular Routes

As your app grows, routes become messy. Router helps organize them.

The Problem

// All in one file - gets messy fast
app.get('/users', ...);
app.post('/users', ...);
app.get('/users/:id', ...);
app.get('/posts', ...);
app.post('/posts', ...);
app.get('/products', ...);
// 100 more routes...

The Solution: Router

// routes/users.js
const express = require('express');
const router = express.Router();

router.get('/', (req, res) => {
  res.json([{ id: 1, name: 'Alice' }]);
});

router.get('/:id', (req, res) => {
  res.json({ id: req.params.id });
});

router.post('/', (req, res) => {
  res.status(201).json(req.body);
});

module.exports = router;

// app.js
const express = require('express');
const userRoutes = require('./routes/users');

const app = express();
app.use(express.json());

app.use('/api/users', userRoutes);

app.listen(3000);

Project Structure

project/
├── app.js
├── routes/
│   ├── index.js
│   ├── users.js
│   ├── posts.js
│   └── products.js
└── package.json

Multiple Route Files

// routes/posts.js
const router = require('express').Router();

router.get('/', (req, res) => res.json([]));
router.post('/', (req, res) => res.status(201).json(req.body));

module.exports = router;

// routes/products.js
const router = require('express').Router();

router.get('/', (req, res) => res.json([]));

module.exports = router;

// app.js
const userRoutes = require('./routes/users');
const postRoutes = require('./routes/posts');
const productRoutes = require('./routes/products');

app.use('/api/users', userRoutes);
app.use('/api/posts', postRoutes);
app.use('/api/products', productRoutes);

Router Index File

// routes/index.js
const express = require('express');
const router = express.Router();

router.use('/users', require('./users'));
router.use('/posts', require('./posts'));
router.use('/products', require('./products'));

module.exports = router;

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

Router-Level Middleware

// routes/admin.js
const router = require('express').Router();

// Middleware for all admin routes
router.use((req, res, next) => {
  if (!req.user?.isAdmin) {
    return res.status(403).json({ error: 'Admin only' });
  }
  next();
});

router.get('/stats', (req, res) => res.json({ users: 100 }));
router.delete('/users/:id', (req, res) => res.json({ deleted: true }));

module.exports = router;

Nested Routes

// routes/users.js
const router = require('express').Router();

router.get('/', (req, res) => res.json([]));

// Nested: /api/users/:userId/posts
router.get('/:userId/posts', (req, res) => {
  const { userId } = req.params;
  res.json({ userId, posts: [] });
});

module.exports = router;

Complete Example

// routes/users.js
const express = require('express');
const router = express.Router();

let users = [{ id: 1, name: 'Alice' }];

router.get('/', (req, res) => {
  res.json(users);
});

router.get('/:id', (req, res) => {
  const user = users.find(u => u.id === +req.params.id);
  if (!user) return res.status(404).json({ error: 'Not found' });
  res.json(user);
});

router.post('/', (req, res) => {
  const user = { id: users.length + 1, ...req.body };
  users.push(user);
  res.status(201).json(user);
});

router.delete('/:id', (req, res) => {
  users = users.filter(u => u.id !== +req.params.id);
  res.status(204).send();
});

module.exports = router;

Key Takeaway

Use express.Router() to split routes into separate files. Mount them with app.use('/path', router). Keeps your code organized as your app grows. Each router is a mini Express app for its routes.