jQuery 简洁几句代码实现图片延迟加载

/*!
 * jquery.scrollLoading.js*/
(function($) {
    $.fn.scrollLoading = function(options) {
        var defaults = {
            attr: "data-original",
            container: $(window),
            callback: $.noop
        };
        var params = $.extend({}, defaults, options || {});
        params.cache = [];
        $(this).each(function() {
            var node = this.nodeName.toLowerCase(), url = $(this).attr(params["attr"]);
            //重组
            var data = {
                obj: $(this),
                tag: node,
                url: url
            };
            params.cache.push(data);
        });
        
        var callback = function(call) {
            if ($.isFunction(params.callback)) {
                params.callback.call(call.get(0));
            }
        };
        //动态显示数据
        var loading = function() {
            
            var contHeight = params.container.height();
            if (params.container.get(0) === window) {
                contop = $(window).scrollTop();
            } else {
                contop = params.container.offset().top;
            }        
            
            $.each(params.cache, function(i, data) {
                var o = data.obj, tag = data.tag, url = data.url, post, posb;
                
                if (o) {
                    post = o.offset().top - contop, posb = post + o.height();
                    if ((post >= 0 && post < contHeight) || (posb > 0 && posb <= contHeight)) {
                        if (url) {
                            //在浏览器窗口内
                            if (tag === "img") {
                                //图片，改变src
                                callback(o.attr("src", url));        
                            } else {
                                o.load(url, {}, function() {
                                    callback(o);
                                });
                            }        
                        } else {
                            // 无地址，直接触发回调
                            callback(o);
                        }
                        data.obj = null;    
                    }
                }
            });    
        };
        
        //事件触发
        //加载完毕即执行
        loading();
        //滚动执行
        params.container.bind("scroll", loading);
    };
})(jQuery);

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>延时加载</title>
<style type="text/css">
body,div,{margin:0;padding:0;}
#box{770px;margin:0 auto;padding:10px 0 0 10px;overflow:hidden;zoom:1;}
#box img{float:left;375px;height:225px;color:#fff;padding:10px 0;display:inline;text-align:center;margin:0 10px 10px 0;background:#000 url(http://fgm.cc/learn/lesson10/img/lazy/loading.gif) 50% 50% no-repeat;}
#box img.loaded{353px;height:225px;vertical-align:middle;}
</style>
</head>
<body>
<div id="box">
    <img src="http://fgm.cc/learn/lesson10/img/lazy/none.gif" data-img="http://fgm.cc/learn/lesson10/img/lazy/1.jpg" />
    <img src="http://fgm.cc/learn/lesson10/img/lazy/none.gif" data-img="http://fgm.cc/learn/lesson10/img/lazy/2.jpg" />
    <img src="http://fgm.cc/learn/lesson10/img/lazy/none.gif" data-img="http://fgm.cc/learn/lesson10/img/lazy/3.jpg" />
    <img src="http://fgm.cc/learn/lesson10/img/lazy/none.gif" data-img="http://fgm.cc/learn/lesson10/img/lazy/4.jpg" />
    <img src="http://fgm.cc/learn/lesson10/img/lazy/none.gif" data-img="http://fgm.cc/learn/lesson10/img/lazy/5.jpg" />
    <img src="http://fgm.cc/learn/lesson10/img/lazy/none.gif" data-img="http://fgm.cc/learn/lesson10/img/lazy/6.jpg" />
    <img src="http://fgm.cc/learn/lesson10/img/lazy/none.gif" data-img="http://fgm.cc/learn/lesson10/img/lazy/7.jpg" />
    <img src="http://fgm.cc/learn/lesson10/img/lazy/none.gif" data-img="http://fgm.cc/learn/lesson10/img/lazy/8.jpg" />
    <img src="http://fgm.cc/learn/lesson10/img/lazy/none.gif" data-img="http://fgm.cc/learn/lesson10/img/lazy/9.jpg" />
    <img src="http://fgm.cc/learn/lesson10/img/lazy/none.gif" data-img="http://fgm.cc/learn/lesson10/img/lazy/10.jpg" />
    <img src="http://fgm.cc/learn/lesson10/img/lazy/none.gif" data-img="http://fgm.cc/learn/lesson10/img/lazy/11.jpg" />
    <img src="http://fgm.cc/learn/lesson10/img/lazy/none.gif" data-img="http://fgm.cc/learn/lesson10/img/lazy/12.jpg" />
    <img src="http://fgm.cc/learn/lesson10/img/lazy/none.gif" data-img="http://fgm.cc/learn/lesson10/img/lazy/13.jpg" />
    <img src="http://fgm.cc/learn/lesson10/img/lazy/none.gif" data-img="http://fgm.cc/learn/lesson10/img/lazy/14.jpg" />
    <img src="http://fgm.cc/learn/lesson10/img/lazy/none.gif" data-img="http://fgm.cc/learn/lesson10/img/lazy/15.jpg" />
    <img src="http://fgm.cc/learn/lesson10/img/lazy/none.gif" data-img="http://fgm.cc/learn/lesson10/img/lazy/16.jpg" />
    <img src="http://fgm.cc/learn/lesson10/img/lazy/none.gif" data-img="http://fgm.cc/learn/lesson10/img/lazy/17.jpg" />
    <img src="http://fgm.cc/learn/lesson10/img/lazy/none.gif" data-img="http://fgm.cc/learn/lesson10/img/lazy/18.jpg" />
    <img src="http://fgm.cc/learn/lesson10/img/lazy/none.gif" data-img="http://fgm.cc/learn/lesson10/img/lazy/19.jpg" />
    <img src="http://fgm.cc/learn/lesson10/img/lazy/none.gif" data-img="http://fgm.cc/learn/lesson10/img/lazy/20.jpg" />
    <img src="http://fgm.cc/learn/lesson10/img/lazy/none.gif" data-img="http://fgm.cc/learn/lesson10/img/lazy/21.jpg" />
    <img src="http://fgm.cc/learn/lesson10/img/lazy/none.gif" data-img="http://fgm.cc/learn/lesson10/img/lazy/22.jpg" />
    <img src="http://fgm.cc/learn/lesson10/img/lazy/none.gif" data-img="http://fgm.cc/learn/lesson10/img/lazy/23.jpg" />
    <img src="http://fgm.cc/learn/lesson10/img/lazy/none.gif" data-img="http://fgm.cc/learn/lesson10/img/lazy/24.jpg" />
    <img src="http://fgm.cc/learn/lesson10/img/lazy/none.gif" data-img="http://fgm.cc/learn/lesson10/img/lazy/25.jpg" />
    <img src="http://fgm.cc/learn/lesson10/img/lazy/none.gif" data-img="http://fgm.cc/learn/lesson10/img/lazy/26.jpg" />
    <img src="http://fgm.cc/learn/lesson10/img/lazy/none.gif" data-img="http://fgm.cc/learn/lesson10/img/lazy/27.jpg" />
    <img src="http://fgm.cc/learn/lesson10/img/lazy/none.gif" data-img="http://fgm.cc/learn/lesson10/img/lazy/28.jpg" />
    <img src="http://fgm.cc/learn/lesson10/img/lazy/none.gif" data-img="http://fgm.cc/learn/lesson10/img/lazy/29.jpg" />
    <img src="http://fgm.cc/learn/lesson10/img/lazy/none.gif" data-img="http://fgm.cc/learn/lesson10/img/lazy/30.jpg" />
</div>


<script src="http://code.jquery.com/jquery-1.8.2.min.js"></script>
<script type="text/javascript">
$(function(){
    showimg();//加载第一屏
    $(window).scroll(function(){
        showimg();//显示当前滚动位置一下两屏且没有被加载的图片
    });
});
function showimg(){
    var vtop=$(document).scrollTop();//滚动条滚动的距离
    var wheight=$(window).height();//窗口高度　
    $("#box img").each(function(){//遍历img
        var truesrc=$(this).attr("data-img");//获取真实图片地址
        if(truesrc&&$(this).offset().top<=(wheight+vtop)){ //如果truesrc存在且有值的时候加载。
            $(this).attr("src",truesrc).removeAttr("data-img");//赋值真实图片地址并移除truesrc属性防止重复加载。
        }
    });
}
</script>
</body>
</html>

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原文地址：https://www.cnblogs.com/huanlei/p/2741850.html