promise.js

'use strict';

let getUrl= (url) => {

  // return a new Promise.
  return new Promise((resolve, reject) => {
    let req = new XMLHttpRequest();
    req.open('GET', url);

    // this is where the magic happens.
    req.onload = () => {
      if (req.status == 200) {
        resolve(req);
      } else {
        reject(req.status);
      }
    };

    // Handle network error
    req.onerror = () => {
      reject(Error('Network is shitty. Whoops. Fuck.'));
    };

    // Makes the request
    req.send();
  });
};

getUrl('https://api.github.com/users/Gusbenz').then((res) => {
  console.log('Success!', res.status);
})
.catch((res) => {
  console.error('Error', res);
});