javascript滑动图片代码，求详细解释每一句的作用，急用，请帮忙

Question

/**///选择器
function $a(id,tag){var re=(id&&typeof id!="string")?id:document.getElementById(id);if(!tag){return re;}else{return re.getElementsByTagName(tag);}}

//焦点滚动图 点击移动
function movec()
{
var o=$a("bd1lfimg","");
var oli=$a("bd1lfimg","dl");
var oliw=oli[0].offsetWidth; //每次移动的宽度

var ow=o.offsetWidth-2;
var dnow=0; //当前位置

var olf=oliw-(ow-oliw+10)/2;
o["scrollLeft"]=olf+(dnow*oliw);
var rqbd=$a("bd1lfsj","ul")[0];
var extime;

<!--for(var i=1;i"+i+"";}-->8
var rq=$a("bd1lfsj","li");
for(var i=0;i<rq.length;i++){reg(i);};
oli[dnow].className=rq[dnow].className="show";
var wwww=setInterval(uu,2000);

function reg(i){rq[i].onclick=function(){oli[dnow].className=rq[dnow].className="";dnow=i;oli[dnow].className=rq[dnow].className="show";mv();}}
function mv(){clearInterval(extime);clearInterval(wwww);extime=setInterval(bc,15);wwww=setInterval(uu,4000);}
function bc()
{
var ns=((dnow*oliw+olf)-o["scrollLeft"]);
var v=ns>0?Math.ceil(ns/10):Math.floor(ns/10);
o["scrollLeft"]+=v;if(v==0){clearInterval(extime);oli[dnow].className=rq[dnow].className="show";v=null;}
}
function uu()
{
if(dnow<oli.length-2)
{
oli[dnow].className=rq[dnow].className="";
dnow++;
oli[dnow].className=rq[dnow].className="show";
}
else{oli[dnow].className=rq[dnow].className="";dnow=0;oli[dnow].className=rq[dnow].className="show";}
mv();
}
o.onmouseover=function(){clearInterval(extime);clearInterval(wwww);}
o.onmouseout=function(){extime=setInterval(bc,15);wwww=setInterval(uu,4000);}
}