Question

I am writing a firefox extension that intercepts the XMLHttpRequest before the page gets loaded in the browser. What I have found so far requires me to create a new instance of XMLHttpRequest.

Any advice on this? Any help will be greatly appreciated!

Answer 1

Override the prototype of the XHR object, eg:

//Capture the original XHR.open method
var _XMLHTTPRequest_open = XMLHttpRequest.prototype.open;

//Overwrite the XHR.open method
XMLHttpRequest.prototype.open = function(){
    //Do something, checks, etc.
    //If permitted:
    _XMLHTTPRequest_open.apply(this, arguments);
}