xhr.js

function xhr($url, $type, $data) {
  var xmlhttp;

  try {
    xmlhttp = new ActiveXObject("Msxml2.XMLHTTP");
  } catch (e) {
    try {
      xmlhttp = new ActiveXObject("Microsoft.XMLHTTP");
    } catch (E) {
      xmlhttp = false;
    };
  };

  if (!xmlhttp && typeof XMLHttpRequest !== undefined) {
    xmlhttp = new XMLHttpRequest();
  };

  xmlhttp.open($type, $url, true);
  xmlhttp.onreadystatechange = function () {
    if (xmlhttp.readyState === 4 && xmlhttp.status === 200) {
      // this code
    }
  };
  
  if ($type === 'POST') {
    xmlhttp.send($data);
  } else {
    xmlhttp.send(null);
  }
}

// init
xhr('link', 'POST', 'params').then(
  function(response) {}, //success state
  function(error) {} //fail state
);