;(function () {
 var open = window.XMLHttpRequest.prototype.open,
  send = window.XMLHttpRequest.prototype.send,
  onReadyStateChange;
 
 function openReplacement(method, url, async, user, password) {
  // some code
 
  return open.apply(this, arguments);
 }
 
 function sendReplacement(data) {
  // some code
 
  if(this.onreadystatechange) this._onreadystatechange = this.onreadystatechange;
  this.onreadystatechange = onReadyStateChangeReplacement;
 
  return send.apply(this, arguments);
 }
 
 function onReadyStateChangeReplacement() {
  // some code
 
  if (this._onreadystatechange) return this._onreadystatechange.apply(this, arguments);
 }
 
 window.XMLHttpRequest.prototype.open = openReplacement;
 window.XMLHttpRequest.prototype.send = sendReplacement;
})();

;(function() {
 function ajaxEventTrigger(event) {
  var ajaxEvent = new CustomEvent(event, { detail: this });
  window.dispatchEvent(ajaxEvent);
 }
  
 var oldXHR = window.XMLHttpRequest;
 
 function newXHR() {
  var realXHR = new oldXHR();
 
  realXHR.addEventListener('abort', function () { ajaxEventTrigger.call(this, 'ajaxAbort'); }, false);
 
  realXHR.addEventListener('error', function () { ajaxEventTrigger.call(this, 'ajaxError'); }, false);
 
  realXHR.addEventListener('load', function () { ajaxEventTrigger.call(this, 'ajaxLoad'); }, false);
 
  realXHR.addEventListener('loadstart', function () { ajaxEventTrigger.call(this, 'ajaxLoadStart'); }, false);
 
  realXHR.addEventListener('progress', function () { ajaxEventTrigger.call(this, 'ajaxProgress'); }, false);
 
  realXHR.addEventListener('timeout', function () { ajaxEventTrigger.call(this, 'ajaxTimeout'); }, false);
 
  realXHR.addEventListener('loadend', function () { ajaxEventTrigger.call(this, 'ajaxLoadEnd'); }, false);
 
  realXHR.addEventListener('readystatechange', function() { ajaxEventTrigger.call(this, 'ajaxReadyStateChange'); }, false);
 
  return realXHR;
 }
 
 window.XMLHttpRequest = newXHR;
})();

var xhr = new XMLHttpRequest();
 
window.addEventListener('ajaxReadyStateChange', function (e) {
 console.log(e.detail); // XMLHttpRequest Object
});
window.addEventListener('ajaxAbort', function (e) {
 console.log(e.detail.responseText); // XHR 返回的内容
});
 
xhr.open('GET', 'info.json');
xhr.send();

;(function () {
 if ( typeof window.CustomEvent === "function" ) return false;
 
 function CustomEvent ( event, params ) {
  params = params || { bubbles: false, cancelable: false, detail: undefined };
  var evt = document.createEvent( 'CustomEvent' );
  evt.initCustomEvent( event, params.bubbles, params.cancelable, params.detail );
  return evt;
 }
 
 CustomEvent.prototype = window.Event.prototype;
 
 window.CustomEvent = CustomEvent;
})();
;(function () {
 function ajaxEventTrigger(event) {
  var ajaxEvent = new CustomEvent(event, { detail: this });
  window.dispatchEvent(ajaxEvent);
 }
  
 var oldXHR = window.XMLHttpRequest;
 
 function newXHR() {
  var realXHR = new oldXHR();
 
  realXHR.addEventListener('abort', function () { ajaxEventTrigger.call(this, 'ajaxAbort'); }, false);
 
  realXHR.addEventListener('error', function () { ajaxEventTrigger.call(this, 'ajaxError'); }, false);
 
  realXHR.addEventListener('load', function () { ajaxEventTrigger.call(this, 'ajaxLoad'); }, false);
 
  realXHR.addEventListener('loadstart', function () { ajaxEventTrigger.call(this, 'ajaxLoadStart'); }, false);
 
  realXHR.addEventListener('progress', function () { ajaxEventTrigger.call(this, 'ajaxProgress'); }, false);
 
  realXHR.addEventListener('timeout', function () { ajaxEventTrigger.call(this, 'ajaxTimeout'); }, false);
 
  realXHR.addEventListener('loadend', function () { ajaxEventTrigger.call(this, 'ajaxLoadEnd'); }, false);
 
  realXHR.addEventListener('readystatechange', function() { ajaxEventTrigger.call(this, 'ajaxReadyStateChange'); }, false);
 
  return realXHR;
 }
 
 window.XMLHttpRequest = newXHR;
})();