取得元素的左和上偏移量的方法

 function getElementLeft(element) 
{ 
var actualLeft = element.offsetLeft; 
var current = element.offsetParent; 

while (current!==null) 
{ 
actualLeft += current.offsetLeft; 
current = current.offsetParent; 
} 
return actualLeft; 
}

取得元素的左偏移量；

function getElementTop(element) 
{ 
var actualTop = element.offsetTop; 
var current = element.offsetParent; 

while (current!==null) 
{ 
 actualTop += current.offsetTop; 
current = current.offsetParent; 
} 
return actualTop; 
}

取得元素的上偏移量；

利用offsetParent属性在Dom层次中逐级向上回溯，将每个层次偏移量合计。