jquery 滚动加载图片效果的实现代码

/* 滚动加载图片 */
function scrollLoading(){
var st = $(window).scrollTop(), sth = st + $(window).height();
var $targetpics = $("img.scrloadpic");
var len = $targetpics.length;
for(var i=0; i< len; i++)
{
var $temppic = $targetpics.eq(i);
var post = $temppic.position().top;
var posb = post + $temppic.height();

if((post > st && post < sth) || (posb > st && posb < sth))
{

var url = $temppic.attr("xsrc");
if(url != "")
{
$temppic.attr("src", url);
$temppic.attr("xsrc", "");
}
}
}
}