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jQuery 简洁几句代码实现图片延迟加载

2012-10-26 22:01 786 查看 
/*!
* 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{width:770px;margin:0 auto;padding:10px 0 0 10px;overflow:hidden;zoom:1;}
#box img{float:left;width: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{width: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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