javascript 封装的一个实用的焦点图切换效果

<div class="jfocus">
    <div id="jfocuspic">
        <a href="#" style="display:block;">图片一</a>
        <a href="#">图片二</a>
        <a href="#">图片三</a>
        <a href="#">图片四</a>
    </div>
    <ul id="jfocusnum">
        <li class="on">1</li>
        <li>2</li>
        <li>3</li>
        <li>4</li>
    </ul>
</div>

.jfocus{width:300px;height:300px;border:#ccc 1px solid;background-color:#FFF;}#jfocuspic{FILTER: progid:DXImageTransform.Microsoft.Fade (duration=0.5,overlap=1.0 );width:300px;height:200px;overflow:hidden;}#jfocuspic a{display:none; font-size:2em; text-align:center; line-height:200px; font-weight:bold; background-color:#CCC; height:200px; cursor:pointer;}#jfocusnum li{cursor:pointer;height:50px; width:50px; line-height:50px;display:inline-block; color:#000; border:#999 1px solid; text-align:center; background-color:#CCC; float:left; margin:0 5px;}#jfocusnum li.on{color:#f00; font-weight:bold; border:#900 1px solid; font-size:14px;}

function $(id,tag){var re=(id&&typeof id!="string")?id:document.getElementById(id);if(!tag){return re;}else{return re.getElementsByTagName(tag);}}//获取元素对象
function FocusImg(focbox,picobj,numbox,numobj,time){
var n=0;
var imglist=$(focbox,picobj);
var Num=$(numbox,numobj);
function setBg(value){for(var i=0;i<Num.length;i++) Num[i].className=(value==i)?"on":"";}//设置字母列表的样式切换；
function plays(value){
if(document.all) $(focbox).filters[0].Apply();//滤镜
for(i=0;i<Num.length;i++){i==value?imglist[i].style.display="block":imglist[i].style.display="none";}
if(document.all) $(focbox).filters[0].play();
}
function mouse(n){//设置鼠标经过和离开后的事件；
    for(var i=0;i<Num.length;i++){
        (function(n){
        Num[i].onmouseover=imglist[i].onmouseover=function(){clearInterval(autoStart);Mea(n);}
        Num[i].onmouseout=imglist[i].onmouseout=function(){setAuto();}
        })(i);
    }
}
function Mea(value){n=value;mouse(n);setBg(value);plays(value);}
function auto(){n++;if(n>Num.length-1)n=0;    Mea(n);}
function setAuto(){autoStart=setInterval(function(){auto();},time)}
setAuto();
}