<!DOCTYPE html>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>原生Js頁面滾動延遲加載圖片</title>
<style type="text/css">
* 
{
 margin:0;
 padding:0
}
img.scrollLoading 
{
 border:1px solid #ccc;
 display:block;
 margin-top:10px;
}
</style>
</head>
<body>
<div id="content"></div>
</body>
</html>
<script type="text/javascript"> 
var _CalF = { 
 $:function(object){//選擇器 
 if(object === undefined ) return; 
 var getArr = function(name,tagName,attr){ 
 var tagName = tagName || '*', 
 eles = document.getElementsByTagName(tagName), 
 clas = (typeof document.body.style.maxHeight === "undefined") ? "className" : "class";//ie6 
 attr = attr || clas, 
 Arr = []; 
 for(var i=0;i<eles.length;i++){ 
 if(eles[i].getAttribute(attr)==name){ 
 Arr.push(eles[i]); 
 } 
 } 
 return Arr; 
 }; 
 if(object.indexOf('#') === 0){ //#id 
 return document.getElementById(object.substring(1)); 
 }
 else if(object.indexOf('.') === 0){ //.class 
 return getArr(object.substring(1)); 
 }
 else if(object.match(/=/g)){ //attr=name
 return getArr(object.substring(object.search(/=/g)+1),null,object.substring(0,object.search(/=/g))); 
 }
 else if(object.match(/./g)){ //tagName.className 
 return getArr(object.split('.')[1],object.split('.')[0]); 
 } 
 }, 
 getPosition : function(obj) { //獲取元素在頁面里的位置和寬高 
 var top = 0, 
 left = 0, 
 width = obj.offsetWidth, 
 height = obj.offsetHeight; 
 while(obj.offsetParent){ 
 top += obj.offsetTop; 
 left += obj.offsetLeft; 
 obj = obj.offsetParent; 
 } 
 return {"top":top,"left":left,"width":width,"height":height}; 
 } 
}; 
 
//添加圖片list 
var _temp = []; 
for (var i = 1; i < 21; i ++) { 
 _temp.push('<img class="scrollLoading" data-src="http://images.cnblogs.com/cnblogs_com/Darren_code/311197/o_' + i + '.jpg" src="http://images.cnitblog.com/blog/150659/201306/23160223-c81dd9aa9a2a4071a47b0ced2c9118bc.gif" /><br />圖片' + i); 
} 
_CalF.$("#content").innerHTML = _temp.join(""); 
 
function scrollLoad(){ 
 this.init.apply(this, arguments); 
} 
scrollLoad.prototype ={ 
 init : function(className){ 
 var className = "img."+className, 
 imgs = _CalF.$(className), 
 that = this; 
 this.imgs = imgs; 
 that.loadImg(); 
 window.onscroll = function(){ 
 that.time = setTimeout(function(){ 
 that.loadImg(); 
 },400); 
 } 
}, 
loadImg : function(){ 
var imgs = this.imgs.reverse(), //獲取數(shù)組翻轉(zhuǎn) 
len = imgs.length; 
if(imgs.length===0){ 
 clearTimeout(this.time); 
 return; 
} 
for(var j=len-1;j>=0;j--){ //遞減 
 var img = imgs[j], 
 imgTop = _CalF.getPosition(img).top, 
 imgSrc = img.getAttribute("data-src"), 
 offsetPage = window.pageYOffset ? window.pageYOffset : window.document.documentElement.scrollTop,//滾動條的top值 
 bodyHeight = document.documentElement.clientHeight; //body的高度 
 if((offsetPage+bodyHeight/2) > (imgTop-bodyHeight/2)){ 
 img.src = imgSrc; 
 this.imgs.splice(j,1); 
 } 
 } 
 } 
} 
 
var img1 = new scrollLoad("scrollLoading"); 
</script>

希望本文所述對大家學(xué)習(xí)javascript程序設(shè)計有所幫助。

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