js图片加载完成前显示loading

<html>  
<title>js图片未加载完显示loading效果</title>  
<body>  
<style>  
img{float:left;width:200px;height:200px;margin:0 10px 10px 0}  
</style>  
<script>  
//判断浏览器  
var Browser=new Object();  
Browser.userAgent=window.navigator.userAgent.toLowerCase();  
Browser.ie=/msie/.test(Browser.userAgent);  
Browser.Moz=/gecko/.test(Browser.userAgent);  

//判断是否加载完成  
function Imagess(url,imgid,callback){      
    var val=url;  
    var img=new Image();  
    if(Browser.ie){  
        img.onreadystatechange =function(){    
            if(img.readyState=="complete"||img.readyState=="loaded"){  
                callback(img,imgid);  
            }  
        }          
    }else if(Browser.Moz){  
        img.onload=function(){  
            if(img.complete==true){  
                callback(img,imgid);  
            }  
        }          
    }      
    //如果因为网络或图片的原因发生异常，则显示该图片  
    img.onerror=function(){img.src="http://www.86y.org/images/failed.png"}  
    img.src=val;  
}  

//显示图片  
function checkimg(obj,imgid){  
document.getElementById(imgid).style.cssText="";  
document.getElementById(imgid).src=obj.src;  
}  
//初始化需要显示的图片，并且指定显示的位置  
window.onload=function(){  
var imglist=document.getElementById("imagelist").getElementsByTagName('img');  
for(i=0;i<imglist.length;i++)  
{  
    imglist[i].id="img0"+i;  
    //imglist[i].src="http://www.86y.org/images/loading.gif";  
    imglist[i].style.cssText="background:url(http://www.86y.org/images/loading.gif) no-repeat center center;"  
    Imagess(imglist[i].getAttribute("data"),imglist[i].id,checkimg);  
}  
}  
</script>  
<div id="imagelist">  
<img data="http://www.smashingapps.com/wp-content/uploads/2013/05/uikitsforwebmobile17s.jpg" />  
<img data="http://www.smashingapps.com/wp-content/uploads/2013/05/uikitsforwebmobile13.jpg" />  
<img data="http://www.smashingapps.com/wp-content/uploads/2013/05/uikitsforwebmobile39.jpg" />  
<img data="http://www.smashingapps.com/wp-content/uploads/2013/05/uikitsforwebmobile10.jpg" />  
<img data="http://www.smashingapps.com/wp-content/uploads/2013/05/uikitsforwebmobile14.jpg" />  
</div>  
</body>  
</html>
js图片加载完成前显示loading

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