JS判断页面是否出现滚动条的方法

var isScroll = function (el) {   // test targets   var elems = el ? [el] : [document.documentElement, document.body];   var scrollX = false, scrollY = false;   for (var i = 0; i < elems.length; i++) {     var o = elems[i];     // test horizontal     var sl = o.scrollLeft;     o.scrollLeft += (sl > 0) ? -1 : 1;     o.scrollLeft !== sl && (scrollX = scrollX || true);     o.scrollLeft = sl;     // test vertical     var st = o.scrollTop;     o.scrollTop += (st > 0) ? -1 : 1;     o.scrollTop !== st && (scrollY = scrollY || true);     o.scrollTop = st;   }   // ret   return {     scrollX: scrollX,     scrollY: scrollY   }; };