A marquee written in js

function cls_marquee(id,id1,id2,sp){
    this.obj_id=id;
    this.obj_id1=id1;
    this.obj_id2=id2;
    this.speed=sp;
    eval(this.obj_id2+".innerHTML="+this.obj_id1+".innerHTML");
   
     function Marquee(){
       if(eval(id2).offsetTop-eval(id).scrollTop<=0)
              eval(id).scrollTop-=eval(id1).offsetHeight
          else{
              eval(id).scrollTop++
            }
            }
         var MyMar=setInterval(Marquee,sp)
         eval(this.obj_id).onmouseover=function() {clearInterval(MyMar)}
         eval(this.obj_id).onmouseout=function() {MyMar=setInterval(Marquee,sp)}
  }

自己刚写的一个小程序，写得满一般的。。。。不过这个接口还成