What is a route in Express?

Node.jsJunior~1 min read

1. What a route is

A route in Express.js is a mapping between:

an HTTP method (GET, POST, PUT, DELETE, …);

a URL path (/, /users, /api/products/:id);

and a handler function, that runs when a request matches it.

In other words, a route tells Express: "If a request for GET /users comes in, run this code."

The simplest route example

javascript

const express = require('express');
const app = express();

app.get('/', (req, res) => {
  res.send('Home page');
});

app.get('/about', (req, res) => {
  res.send('About us');
});

app.listen(3000, () => console.log('Server running'));

If you open these in a browser:

http://localhost:3000/ → Home page
http://localhost:3000/about → About us

2. A route's format

javascript

app.METHOD(PATH, HANDLER)

Element	What it is	Example
`METHOD`	The HTTP method (lowercase)	`get`, `post`, `put`, `delete`
`PATH`	The path the route responds to	`'/'`, `'/users'`, `'/users/:id'`
`HANDLER`	The `(req, res)` handler function	`(req, res) => res.send('OK')`

3. Examples of different routes

GET, retrieve data

javascript

app.get('/users', (req, res) => {
  res.send('List of users');
});

POST, create

javascript

app.post('/users', (req, res) => {
  res.send('User created');
});

PUT, update

javascript

app.put('/users/:id', (req, res) => {
  res.send(`User ${req.params.id} updated`);
});

DELETE, remove

javascript

app.delete('/users/:id', (req, res) => {
  res.send(`User ${req.params.id} deleted`);
});

4. Dynamic routes

Routes can contain parameters, marked with :name.

javascript

app.get('/products/:id', (req, res) => {
  res.send(`Product with ID: ${req.params.id}`);
});

GET /products/123 → response: Product with ID: 123

Parameters can be read via req.params.

5. Grouping routes (Router)

To keep code organized, it's convenient to move routes into separate files using express.Router():

javascript

const express = require('express');
const router = express.Router();

router.get('/', (req, res) => res.send('List of products'));
router.get('/:id', (req, res) => res.send(`Product ${req.params.id}`));

module.exports = router;

In the main file:

javascript

const productsRouter = require('./routes/products');
app.use('/products', productsRouter);

Now GET /products and GET /products/123 are handled by this module.

6. Routes can have several handlers

You can pass several functions (middleware) that run one after another:

javascript

app.get('/admin',
  (req, res, next) => {
    console.log('Checking authorization...');
    next();
  },
  (req, res) => {
    res.send('Admin panel');
  }
);

7. Support for patterns and RegExp in routes

Express supports pattern routes and regular expressions:

javascript

app.get('/ab*cd', (req, res) => {
  res.send('Matched the pattern /ab*cd');
});

This matches /abcd, /ab123cd, /abXYZcd, and so on.

8. Summary

A route in Express.js is a rule that tells the server how to respond to a specific HTTP request.

It consists of:

an HTTP method (GET, POST, PUT, DELETE, etc.),

a path (/, /users/:id),

a handler function ((req, res)).

Routes:

drive the application's logic;

support dynamic parameters;

can be grouped into modules via Router;

support middleware and pattern paths.

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