Node.js Express Routing

What is Express Routing in Node.js?

Routing maps an HTTP method and path to a handler. Express supports route parameters, query strings, chained handlers and Router instances for splitting a large API into files.

Express Routing example

// routes/jobs.js
import { Router } from 'express';
const router = Router();

router.get('/', listJobs);              // GET  /api/jobs
router.get('/:id', getJob);             // GET  /api/jobs/123
router.post('/', requireAuth, createJob);
router.put('/:id', requireAuth, updateJob);
router.delete('/:id', requireAuth, deleteJob);

export default router;

// index.js
app.use('/api/jobs', jobsRouter);

Reading params, query and body

router.get('/:id', (req, res) => {
  req.params.id;          // '123'  — from the path
  req.query.page;         // '2'    — from ?page=2
  req.body;               // parsed JSON on POST/PUT
  res.json({ id: req.params.id });
});

Key points to remember

• Routes are matched in the order they are registered — put specific paths before parameterised ones.
• A Router keeps each resource in its own file.
• Every param and query value is a string.

Common mistakes with Express Routing

• Declaring /jobs/:id before /jobs/featured, so "featured" is treated as an id.
• Sending two responses in one handler, which throws ERR_HTTP_HEADERS_SENT.