js简单实现图片延迟加载的方法

window.onload=window.onresize=window.onscroll=function(){  showImg();};function getPos(obj){  var l=0;  var t=0;  while(obj)  {    l+=obj.offsetLeft;    t+=obj.offsetTop;    obj=obj.offsetParent;  }  return {left: l, top: t};}function showImg(){  var aTmg=document.getElementsByTagName('img');  var scrollTop=document.documentElement.scrollTop||document.body.scrollTop;  var scrollBottom=scrollTop+document.documentElement.clientHeight;  for(var i=0;i<aTmg.length;i++)  {    var p=getPos(aTmg[i]);    if(p.top<scrollBottom)    {      //alert(aTmg);      aTmg[i].src=aTmg[i].getAttribute('_src');    }  }}