JavaScript "XHR" tutorial

xhr.js

/* References:
   https://developers.google.com/web/updates/2015/03/introduction-to-fetch
   https://www.w3schools.com/xml/xml_http.asp
   https://developer.mozilla.org/en-US/docs/Web/API/XMLHttpRequest
*/

function reqListener() {
  var data = JSON.parse(this.responseText);
  console.log(data);
}

function reqError(err) {
  console.log('Fetch Error :-S', err);
}

var oReq = new XMLHttpRequest();

// setting callback function for 'load' event
// fired when transaction completes successfully.
oReq.onload = reqListener;

// setting callback function for 'error' event
// fired when the request encountered an error
oReq.onerror = reqError;

// initialize request
oReq.open('get', 'https://jsonplaceholder.typicode.com/users', true);

// send async request and returns as soon as the request is send
// then wait for events
oReq.send();