js图片延迟技术一般的思路与示例

2014-03-20 29

图片延迟技术一般的思路

1.现将img元素对应的src路径设置为背景图片,而该img所对应的url路径存放在一个自设的属性中(以便进行src替换)。

2.获取卷轴的高度和窗口的高度

3循环需要延迟加载的img数组,获取img的高度,判断该元素是否在可视窗口内。若该元素在可视窗口内,则进行src替换

一下为测试代码

html

<style> 
.wrap { 
margin: 20px auto; 
width: 150px; 
} 
.wrap div { 
border: 1px dotted #E29808; 
height: 30px; 
line-height: 30px; 
margin: 5px auto; 
text-align: center; 
width: 150px; 
} 
.wrap .sortable { 
background-color: #E6D6AB; 
border: 1px solid #E29808; 
} 
#showImg li{ 
width:30%; 
margin-left:2%; 
margin-top:15px; 
height:300px; 
float:left; 
background:#CCC; 
} 
#showImg li:nth-child(3n){ 
margin-left:3%; 
} 
#showImg li img{ 
width:100%; 
max-height:100%; 
} 
</style> 
</head> <body> 
<div id="showImg"> 
<li><img src="http://img4.duitang.com/uploads/item/201306/08/20130608190125_3kFty.jpeg" alt="test" /></li> 
<li><img src="http://cdn.duitang.com/uploads/item/201306/07/20130607171626_QkC3T.thumb.600_0.jpeg" alt="test" /></li> 
<li><img src="http://i2.sinaimg.cn/gm/2011/0127/U5238P115DT20110127111837.jpg" alt="test" /></li> 
</div> 
</body>

js部分
var imgsglobal=[ 
"http://cdn.duitang.com/uploads/item/201306/07/20130607171626_QkC3T.thumb.600_0.jpeg", 
"http://img4.duitang.com/uploads/item/201306/07/20130607172438_Teijr.jpeg", 
"http://cdn.duitang.com/uploads/item/201306/08/20130608190311_BYwcA.thumb.600_0.jpeg", 
"http://g-ec4.images-amazon.com/images/G/28/BOOK-Catalog/Liaoxiaojun/B003U5TATY_01_AMZN.jpg", 
"http://www.yishun.net/tuysL3R1eXNpbWcwNC50YW9iYW9jZG4uY29tL2ltZ2V4dHJhL2k0Lzc0MDY1MDAzMi9UMl9HbmVYanRhWFhYWFhYWFhfISE3NDA2NTAwMzIuanBn.jpg", 
"http://www.yishun.net/tuysL3R1eXNpbWcwMy50YW9iYW9jZG4uY29tL2ltZ2V4dHJhL2kzLzc0MDY1MDAzMi9UMkVHbF9YaVhjWFhYWFhYWFhfISE3NDA2NTAwMzIuanBn.jpg", 
"http://img4.duitang.com/uploads/item/201306/08/20130608190125_3kFty.jpeg", 
"http://img4.duitang.com/uploads/item/201304/29/20130429142901_SQjJv.thumb.600_0.jpeg", 
"http://img4.duitang.com/uploads/item/201112/04/20111204170801_fiBKm.jpg", 
"http://img2.duitang.com/uploads/item/201211/06/20121106233027_LdQaS.thumb.600_0.jpeg", 
"http://i2.sinaimg.cn/gm/2011/0127/U5238P115DT20110127111837.jpg", 
"http://img2.duitang.com/uploads/item/201209/24/20120924162953_hLPJe.jpeg", 
"http://wenwen.soso.com/p/20110624/20110624085901-745594320.jpg", 
"http://img4.duitang.com/uploads/item/201206/15/20120615185646_uzmrt.thumb.600_0.jpeg", 
"http://img4.duitang.com/uploads/item/201202/11/20120211213039_U4Sj8.thumb.600_0.jpg", 
"http://cdn.duitang.com/uploads/item/201201/25/20120125145922_n4Vz8.thumb.600_0.jpg" 
]; 
function addImgEle(){ 
var str=''; 
for(var i=0, len=imgsglobal.length; i<len; i++){ 
str+='<li><img class="lazyImg" src="wait" resrc="'+imgsglobal[i]+'" /></li>' 
} 
$("#showImg").append(str); 
} 
$(document).ready(function(){ 
addImgEle(); 
}); 
(function(win){ 
var lazyLoad=win['lazyLoad']||{}; 
var camelize = function (s) { 
return s.replace(/-(\w)/g, function (strMatch, p1) { 
return p1.toUpperCase(); 
}); 
}; 
lazyLoad={ 
init:function(ImgClass){ 
var offsetPage = window.pageYOffset ? window.pageYOffset : window.document.documentElement.scrollTop, 
offsetWindow = offsetPage + Number(window.innerHeight ? window.innerHeight : document.documentElement.clientHeight); 
var Imgeles=ImgClass; 
for(var i=0, len=Imgeles.length; i<len; i++){ 
if(Imgeles[i].getAttribute("resrc")=="show"){ 
continue; 
} 
var o=Imgeles[i]; 
if(o){ 
postPage = o.getBoundingClientRect().top + window.document.documentElement.scrollTop +window.document.body.scrollTop; 
postWindow = postPage + Number(this.getStyle(o, 'height').replace('px', '')); 
if ((postPage > offsetPage && postPage < offsetWindow) || (postWindow > offsetPage && postWindow < offsetWindow)){ 
var src=o.getAttribute("resrc"); 
o.setAttribute("src", src); 
o.setAttribute("resrc", "show"); 
} 
} 
} 
}, 
getStyle:function (element, property) { 
if (arguments.length != 2) return false; 
var value = element.style[camelize(property)]; 
if (!value) { 
if (document.defaultView && document.defaultView.getComputedStyle) { 
var css = document.defaultView.getComputedStyle(element, null); 
value = css ? css.getPropertyValue(property) : null; 
} else if (element.currentStyle) { 
value = element.currentStyle[camelize(property)]; 
} 
} 
return value == 'auto' ? '' : value; 
} 
} 
win.lazyLoad=lazyLoad; 
})(window); 
$(document).ready(function(){ 
lazyLoad.init($("img.lazyImg")); 
window.onscroll=function (){ 
lazyLoad.init($("img.lazyImg")); 
} 
});
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