basic node.js server with GET endpoints & without express

basic nodejs server.js

const https = require('https');

callback = returnFn => response => {
  let str = '';
  response.on('data', chunk => {
    str += chunk;
  });
  response.on('end', () => {
    returnFn(str);
  });
}
const backup = (value) => console.log(value)
const getHtmlDoc = (url, returnFn = backup) => https.request(url, callback(returnFn)).end();

const http = require('http');

http.createServer((req, res) => {
  const sendJson = (data) => {
    res.writeHead(200, {'Content-Type': 'application/json'});
    res.write(JSON.stringify(data) );
    res.end();
  }
  const sendHtml = (data) => {
    res.writeHead(200, {'Content-Type': 'text/html'});
    res.write(data);
    res.end();
  }

  switch (req.url) {
    case '/wiki':
      getHtmlDoc('https://www.wikipedia.org/', sendHtml)
      break
    case '/json-data':
      sendJson({ data: [1,2,3] })
      break
    default:
      sendHtml('<h1>Hello World!</h1>')
  }
}).listen(3000, () => {
  console.log("server start at port http://localhost:3000");
});