How to modify ActiveXObject JS constructor?

Question

I need to wrap an IE ajax request to notify me when it happens. ie i need to know when open is called on this:

var xhr = new ActiveXObject("Microsoft.XMLHTTP");

The only way to do that(i think) is to implement the ActiveXObject constructor to proxy open calls to the real constructor/object. Can you help me do that?

also: i dont need to create the actual xhr object, so please dont tell me to use X framework because its easy.

all i need to know is when open is called (not by my code) on an MS xhr object.

Thank you very much!

Answer 1

I recommend you to use jQuery for AJAX . It's very small but very flexible and fast framework. Check out docs here.

Answer 2

Perhaps you can try something like this:

XMLHttpRequest.prototype.real_open = XMLHttpRequest.prototype.open;

var your_open_method = function(sMethod, sUrl, bAsync, sUser, sPassword) { 
  alert('an XHR request has been made!');
  this.real_open(sMethod, sUrl, bAsync, sUser, sPassword); 
} 

XMLHttpRequest.prototype.open = your_open_method;

Of course, instead of the alert you can have your own tracking code. I tried it out and it works on 'plain javascript' requests and also requests made with jquery. I think it should work regardless of the framework that was used to make the request.

EDIT April 21 I don't really know how an ActiveXObject can be extended. My guess is that something like this should work:

XHR = new ActiveXObject("Microsoft.XMLHTTP");
var XHR.prototype.old_open = XHR.prototype.open;
var new_open = function(sMethod, sUrl, bAsync, sUser, sPassword) { 
  alert('an IE XHR request has been made!');
  this.old_open(sMethod, sUrl, bAsync, sUser, sPassword); 
} 

XHR.prototype.open = new_open;

Unfortunately (or maybe not) I don't have IE, so I can't test it. But give it a spin and let me know if it did the trick.

Answer 3

There is nothing "to get at real object" it is the real object!

Sounds like you are looking for something like this guy is doing....

http://www.adobepress.com/articles/article.asp?p=439600

document.write("");

function Ajax() { this.toString = function() { return "Ajax"; } this.http = new HTTP();

this.makeRequest = function(_method, _url, _callbackMethod) { this.request = (window.XMLHttpRequest)? new XMLHttpRequest(): new ActiveXObject("MSXML2.XMLHTTP"); this.request.onreadystatechange = _callbackMethod; this.request.open(_method, _url, true); this.request.send(_url); }

this.checkReadyState = function(_id, _1, _2, _3) { switch(this.request.readyState) { case 1: document.getElementById(_id).innerHTML = _1; break; case 2: document.getElementById(_id).innerHTML = _2; break; case 3: document.getElementById(_id).innerHTML = _3; break; case 4: return this.http.status(this.request.status); } } }

Answer 4

This has always worked for me.

var xmlHttp;

function yourajaxfunction(str)
{ 
   xmlHttp=GetXmlHttpObject();
   if (xmlHttp==null){
      alert ("Browser does not support HTTP Request");
      return;
   }

   var url="yourserversidecodefile.php";
   url=url+"?q="+str;

   xmlHttp.onreadystatechange=stateChanged;
   xmlHttp.open("GET", url, true);
   xmlHttp.send(null);
}

function stateChanged() { 
   if (xmlHttp.readyState==4 || xmlHttp.readyState=="complete"){ 
      document.getElementById("txtHint").innerHTML=xmlHttp.responseText;
   } 
}

function GetXmlHttpObject(){
   var xmlHttp=null;

   try {
      // Firefox, Opera 8.0+, Safari
      xmlHttp=new XMLHttpRequest();
   }
   catch (E1) {
      //Internet Explorer
      try {
         xmlHttp=new ActiveXObject("Msxml2.XMLHTTP");
      }
      catch (E2) {
         xmlHttp=new ActiveXObject("Microsoft.XMLHTTP");
      }
   }

   return xmlHttp;
}

Answer 5

Since the OP has posted a similar question, and I posted an answer which also happens to fit this question, he asked me to link to my answer, instead of repeating it here.

• Q: Extending an ActiveXObject in javascript
• A: A drop-in transparent wrapper for MSXML2.XMLHTTP