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>