jquery实现异步加载图片（懒加载图片一种方式）

 (function($) {         // alert($.fn.scrollLoading);         $.fn.scrollLoading = function(options) {           var defaults = {             attr: "data-url"           };           var params = $.extend({}, defaults, options || {});           params.cache = [];           $(this).each(function() {             var node = this.nodeName.toLowerCase(),               url = $(this).attr(params["attr"]);             if(!url) {               return;             }             var data = {               obj: $(this),               tag: node,               url: url             };             params.cache.push(data);           });            var loading = function() {             var st = $(window).scrollTop(),               sth = st + $(window).height();             $.each(params.cache, function(i, data) {               var o = data.obj,                 tag = data.tag,                 url = data.url;               if(o) {                 post = o.position().top;                 posb = post + o.height();                 if((post > st && post < sth) || (posb > st && posb < sth)) {                   if(tag === "img") {                     o.attr("src", url);                   } else {                     o.load(url);                   }                   data.obj = null;                 }               }             });             return false;           };            loading();           $(window).bind("scroll", loading);         };       })(jQuery);

 $(document).ready(function () {     //实现图片慢慢浮现出来的效果     $("img").load(function () {       //图片默认隐藏        $(this).hide();       //使用fadeIn特效        $(this).fadeIn("5000");     });     // 异步加载图片，实现逐屏加载图片     $(".scrollLoading").scrollLoading();    });

<img class="scrollLoading" data-url="image/logo.jpg" src="images/load.gif" />