Routing

Routing decides what code should run for a specific HTTP request.

A route usually depends on:

• HTTP method,
• URL path.

Basic routes

app.get('/users', (req, res) => {
  res.json([{ id: 1, name: 'Asha' }])
})

app.post('/users', (req, res) => {
  res.status(201).json({ message: 'User created' })
})

GET /users and POST /users are different routes.

They use the same path, but different HTTP methods.

Common HTTP methods

Route params

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

For /users/42, req.params.id is 42.

Router

For larger apps, use express.Router.

import { Router } from 'express'

const router = Router()

router.get('/', getUsers)
router.post('/', createUser)

export default router

Then mount it:

app.use('/users', userRouter)

Common mistake

Route order matters.

Put specific routes before broad dynamic routes.

app.get('/users/me', getCurrentUser)
app.get('/users/:id', getUserById)

If /:id comes first, /me may be treated as an id.

Interview answer

Routing in Express maps an HTTP method and path to a handler function. For example, GET /users can return users, while POST /users can create a user. Express Router helps split routes into separate modules for maintainability.