//獲取元素的縱坐標
function getTop(e){
var offset=e.offsetTop;
if(e.offsetParent!=null) offset+=getTop(e.offsetParent);
return offset;
}
//獲取元素的橫坐標
function getLeft(e){
var offset=e.offsetLeft;
if(e.offsetParent!=null) offset+=getLeft(e.offsetParent);
return offset;
}