Emulate jQuery's AjaxStart and AjaxEnd for native javascript

This is a javascript code that will be injected into every page a .NET WebBrowser component navigates to. This means the code needs to be compatible with IE 7+ only. The code will be injected and run when the OnNavigateComplete event happens, which means it will run before any other script in the page runs.

ajaxHandler is an object defined in another section with only two methods: OnAjaxStart and OnAjaxEnd.

The requirements are that ajaxHandler.OnAjaxStart should be called before one or more ajax requests start and ajaxHandler.OnAjaxEnd must be called after these ajax calls end. Also, there must be a call to ajaxHandler.OnAjaxEnd for every call to ajaxHandler.OnAjaxStart so the application doesn't wait for the ajax call to end forever (unless the page itself waits forever; this could safely be considered as a page that doesn't complete loading). Finally, the code shouldn't mess with the webpage's functionality.

This is all part of a web scrapping application and the goal is to have the web scraper wait until AJAX completes before it starts getting data from the page (any page).

(function () {
    if (!(window.____hsXMLHttpRequestHooked === true)) {
        window.____hsXMLHttpRequestHooked = true;

        function arrayRemove(array, from, to) {
            var rest = array.slice((to || from) + 1 || array.length);
            array.length = from < 0 ? array.length + from : from;
            return array.push.apply(array, rest);
        }

        function addRequest(request) {
            if (requests.length == 0) ajaxHandler.OnAjaxStart(window);
            for (var i = 0; i < requests.length; i++) {
                if (requests[i] == request) return;
            }
            requests.push(request);
        }

        function removeRequest(request) {
            for (var i = 0; i < requests.length; i++) {
                if (requests[i] == request) {
                    arrayRemove(requests, i);
                    break;
                }
            }
            if (requests.length == 0) ajaxHandler.OnAjaxEnd(window);
        }

        var oldSend = XMLHttpRequest.prototype.send;
        var requests = [];

        XMLHttpRequest.prototype.send = function () {
            var originalCallback = this.onreadystatechange;
            this.onreadystatechange = function () {
                if (originalCallback) originalCallback.apply(this, [].slice.call(arguments));
                if (this.readyState == 4) removeRequest(this);
            }
            addRequest(this);
            oldSend.apply(this, [].slice.call(arguments));
        } 
    }
})();