server.js

'use strict';

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

const PORT = 8000;
const HANDLER_LENGTH = 3;

const user = { name: 'jura', age: 22 };

const routing = {
  '/': '<h1>welcome to homepage</h1><hr>',
  '/user': user,
  '/user/name': () => user.name.toUpperCase(),
  '/user/age': () => user.age,
  '/hello': { hello: 'world', andArray: [1, 2, 3, 4, 5, 6, 7] },
  '/api/method1': (req, res, callback) => {
    console.log(req.url + ' ' + res.statusCode);
    callback({ status: res.statusCode });
  },
  '/api/method2': (req) => ({
    user,
    url: req.url,
    cookie: req.headers.cookie,
  }),
};

const types = {
  object: ([data], callback) => callback(JSON.stringify(data)),
  undefined: (args, callback) => callback('not found'),
  function: ([fn, req, res], callback) => {
    if (fn.length === HANDLER_LENGTH) fn(req, res, callback);
    else callback(JSON.stringify(fn(req, res)));
  },
};

const serve = (data, req, res) => {
  const type = typeof data;
  if (type === 'string') return void res.end(data);
  const serializer = types[type];
  serializer([data, req, res], (ser) => serve(ser, req, res));
};

http
  .createServer((req, res) => {
    const data = routing[req.url];
    serve(data, req, res);
  })
  .listen(PORT);

setInterval(() => user.age++, 2000);