jQuery XDR for IE

jquery.xdr.js

(function ($) {
    "use strict";
    if (window.XDomainRequest) {
        $.ajaxTransport(function(s) {
            if (s.crossDomain && s.async) {
                if (s.timeout) {
                    s.xdrTimeout = s.timeout;
                    delete s.timeout;
                }
                var xdr;
                return {
                    send: function(_, complete) {
                        function callback(status, statusText, responses, responseHeaders) {
                            xdr.onload = xdr.onerror = xdr.ontimeout = $.noop;
                            xdr = undefined;
                            complete(status, statusText, responses, responseHeaders);
                        }
                        xdr = new XDomainRequest();
                        xdr.onload = function() {
                            callback(200, "OK", { text: xdr.responseText }, "Content-Type: " + xdr.contentType);
                        };
                        xdr.onerror = function() {
                            callback(404, "Not Found");
                        };
                        xdr.onprogress = function () {};
                        xdr.ontimeout = function() {
                            callback(0, "timeout");
                        };
                        xdr.timeout = s.xdrTimeout || Number.MAX_VALUE;
                        xdr.open(s.type, s.url);
                        xdr.send((s.hasContent && s.data) || null);
                    },
                    abort: function() {
                        if (xdr) {
                            xdr.onerror = $.noop;
                            xdr.abort();
                        }
                    }
                };
            }
        });
    }
})(jQuery);

Wonderful work.
However, I had issues with in in IE9 when it's in IE8 compatibility mode (even though it works fine in IE8 itself).
This worked for me in the end: https://github.com/MoonScript/jQuery-ajaxTransport-XDomainRequest/blob/master/jQuery.XDomainRequest.js