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

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

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.