Routing

What is routing?

Routing is the process of deciding which piece of code handles a given HTTP request. The decision is based on two properties of the request:

req.method — the HTTP verb: GET, POST, PUT, DELETE, etc.
req.url — the path (and optional query string): /users, /users/42, /search?q=node

Node’s built-in server gives you both. You write the logic that maps them to handlers.

Manual routing with if/else

The simplest router is a chain of if statements:

Node.js

const http = require('node:http');

const server = http.createServer(function(req, res) {
  const method = req.method;
  const url = req.url;

  if (method === 'GET' && url === '/') {
    res.writeHead(200, { 'Content-Type': 'text/plain' });
    res.end('GET / - Home');
  } else if (method === 'GET' && url === '/about') {
    res.writeHead(200, { 'Content-Type': 'text/plain' });
    res.end('GET /about - About page');
  } else if (method === 'POST' && url === '/users') {
    res.writeHead(201, { 'Content-Type': 'text/plain' });
    res.end('POST /users - Created a user');
  } else {
    res.writeHead(404, { 'Content-Type': 'text/plain' });
    res.end('404 Not Found');
  }
});

server.listen(3000, function() {
  console.log('Router running at http://localhost:3000');
});

Needs the Node.js runtime — open in StackBlitz to run.

Parsing the URL with the URL class

When URLs contain path parameters or query strings, use Node’s global URL constructor to parse them cleanly. Pass req.url as the first argument and a fake base as the second:

Node.js

const http = require('node:http');

const server = http.createServer(function(req, res) {
  // Use the global URL class to parse the request URL
  const parsed = new URL(req.url, 'http://localhost:3000');
  const pathname = parsed.pathname;   // e.g. '/search'
  const query = parsed.searchParams;  // URLSearchParams

  if (req.method === 'GET' && pathname === '/search') {
    const term = query.get('q') || '(none)';
    res.writeHead(200, { 'Content-Type': 'text/plain' });
    res.end('Search term: ' + term);
  } else {
    res.writeHead(404, { 'Content-Type': 'text/plain' });
    res.end('404 Not Found');
  }
});

server.listen(3000, function() {
  console.log('Try: http://localhost:3000/search?q=nodejs');
});

Needs the Node.js runtime — open in StackBlitz to run.

A tiny router object

Once you have more than a few routes, extract them into a router map. This is exactly the pattern that Express uses internally:

Node.js

const http = require('node:http');

// Route map: keys are "METHOD /path"
const routes = {
  'GET /': function(req, res) {
    res.writeHead(200, { 'Content-Type': 'text/plain' });
    res.end('Home');
  },
  'GET /users': function(req, res) {
    res.writeHead(200, { 'Content-Type': 'application/json' });
    res.end(JSON.stringify([{ id: 1, name: 'Alice' }]));
  },
  'POST /users': function(req, res) {
    res.writeHead(201, { 'Content-Type': 'application/json' });
    res.end(JSON.stringify({ created: true }));
  },
};

const server = http.createServer(function(req, res) {
  const key = req.method + ' ' + new URL(req.url, 'http://x').pathname;
  const handler = routes[key];

  if (handler) {
    handler(req, res);
  } else {
    res.writeHead(404, { 'Content-Type': 'text/plain' });
    res.end('404 Not Found: ' + key);
  }
});

server.listen(3000, function() {
  console.log('Tiny router running at http://localhost:3000');
});

Needs the Node.js runtime — open in StackBlitz to run.