用 Javascript 获取指定页面元素的位置

<script language="javascript" type="text/javascript">

<!--  

// 说明：用 Javascript 获取指定页面元素的位置 

// 整理：http://www.codebit.cn 

// 来源：YUI DOM  

function getElementPos(elementId) {

	var ua = navigator.userAgent.toLowerCase();     

	var isOpera = (ua.indexOf('opera') != -1);     

	var isIE = (ua.indexOf('msie') != -1 && !isOpera); // not opera spoof      

	var el = document.getElementById(elementId); 

	    

	if(el.parentNode === null || el.style.display == 'none'){ return false; }      

	var parent = null;

	var pos = [];     //不定长数组？

	var box;      

	if(el.getBoundingClientRect){  //IE     

		box = el.getBoundingClientRect();        

		var scrollTop = Math.max(document.documentElement.scrollTop, document.body.scrollTop);        

	    var scrollLeft = Math.max(document.documentElement.scrollLeft, document.body.scrollLeft);          

 		return {x:box.left + scrollLeft, y:box.top + scrollTop};     

	}else if(document.getBoxObjectFor){   // gecko       	      

 		box = document.getBoxObjectFor(el);                     

  		var borderLeft = (el.style.borderLeftWidth)?parseInt(el.style.borderLeftWidth):0;         

 		var borderTop = (el.style.borderTopWidth)?parseInt(el.style.borderTopWidth):0;          

  		pos = [box.x - borderLeft, box.y - borderTop];     

	}else{    // safari & opera     

        pos = [el.offsetLeft, el.offsetTop];        

	    parent = el.offsetParent;         

		if (parent != el) {

			while (parent) {                 

				pos[0] += parent.offsetLeft;               

			    pos[1] += parent.offsetTop;             

				parent = parent.offsetParent;            

			}

		}         

		if (ua.indexOf('opera') != -1  || ( ua.indexOf('safari') != -1 && el.style.position == 'absolute' )){              

			pos[0] -= document.body.offsetLeft;             

			pos[1] -= document.body.offsetTop;         

		}      

	}            

	if (el.parentNode) { 

		parent = el.parentNode; 

	} else { 

		parent = null; 

	}       

	while (parent && parent.tagName != 'BODY' && parent.tagName != 'HTML') { // account for any scrolled ancestors        

		pos[0] -= parent.scrollLeft;         

		pos[1] -= parent.scrollTop;      

		if (parent.parentNode) { 

			parent = parent.parentNode; 

		} else { 

			parent = null; 

		}     

	}     

	return {x:pos[0], y:pos[1]};

}  //--> 

</script>