1 function getScrollTop() { 2     var scrollPos;  3     if (window.pageYOffset) { 4     scrollPos = window.pageYOffset;  5     }else if (document.compatMode && document.compatMode != 'BackCompat') {  6             scrollPos = document.documentElement.scrollTop; }  7     else if (document.body) {  8             scrollPos = document.body.scrollTop;  9         } return scrollPos; 10 }