让 DOM IE 变得友好

我怎样才能使这个脚本对IE友好？唯一对 IE 不友好的部分是变量scrolledtonum and heightofbody...

function getheight() {

            var myWidth = 0,
        myHeight = 0;
         if (typeof (window.innerWidth) == 'number') {
                //Non-IE
                myWidth = window.innerWidth;
                myHeight = window.innerHeight;
            } else if (document.documentElement && (document.documentElement.clientWidth || document.documentElement.clientHeight)) {
                //IE 6+ in 'standards compliant mode'
                myWidth = document.documentElement.clientWidth;
                myHeight = document.documentElement.clientHeight;
            } else if (document.body && (document.body.clientWidth || document.body.clientHeight)) {
                //IE 4 compatible
                myWidth = document.body.clientWidth;
                myHeight = document.body.clientHeight;
            }
            var scrolledtonum = window.pageYOffset + myHeight + 2;
            var heightofbody = document.body.offsetHeight;
            if (scrolledtonum >= heightofbody) {
                document.body.scrollTop = 0;
            }
        }

        window.onscroll = getheight; 

        function func() {
            window.document.body.scrollTop++;
        }

        window.document.onmouseover = function () {
            clearInterval(interval);
        };

        window.document.onmouseout = function () {
            interval = setInterval(func, 20);
        };

        var interval = setInterval(func, 20);

关于scrollY 的mozilla MDN 文档包含用于处理pageYOffset 兼容性问题的示例代码：https://developer.mozilla.org/En/DOM/Window.scrollY https://developer.mozilla.org/En/DOM/Window.scrollY.

它说如下：

为了跨浏览器兼容性，请使用window.pageYOffset代替window.scrollY，除了使用

(((t = document.documentElement) || (t = document.body.parentNode)) && typeof t.ScrollTop == 'number' ? t : document.body).ScrollTop

when window.pageYOffset (and window.scrollY) 未定义。