Does XMLHttpRequest work the same in IE7 as it doesn IE8?

Would the following code work the same?

Code:
  $objX = new XMLHttpRequest();

        if ($objX != null) {

            $objX.open("GET", "json/low-resulution-images.json ", true);

            $objX.onreadystatechange = function () {

                //if readyState is not 4 or or status not 200 then there is a problem that needs attending
                if ($objX.readyState !== 4) {

                    if ($objX.status !== 200) {

                        alert('HTTP error ' + $objX.status);

                    }

                }

            };

            $objX.send();

            alert($objX.responseText);

        } else {

            window.alert("AJAX  not supported.");

        }
I don't have a native version of IE7 so it is difficult for me to test for sure