Simple ajax lib

ajax.js

  function ajax(url, cb, postData) {
    var request = window.ActiveXObject ? new ActiveXObject('Microsoft.XMLHTTP') : new XMLHttpRequest();

    request.onreadystatechange = function () {
      console.log('what');
      if (request.readyState==4)
        cb(request.responseText);
    };

    if (postData) {
      request.open("POST", url, true);
      request.setRequestHeader('Content-type', 'application/x-www-form-urlencoded');
      request.setRequestHeader('Connection', 'close');
    } else {
      request.open("GET", url, true);
    }
    request.setRequestHeader('X-Requested-With', 'XMLHttpRequest');

    request.send(postData || '');
  }