document.onkeyup=function(event){
        event=event||window.event;
        //向下
        if(event.keyCode==40){
            index++;
        if(index>(as.length)-1){
            index=0;
        for(var i=0,l=as.length;i<l;i++){
            as[i].style.background="#fff";
        }
        }

        as[index].style.background="#567";
        as[index-1].style.background="#fff";


        }
        //向上
        if(event.keyCode==38){
            index--;
        if(index<0){
            index=as.length-1;
        for(var i=0,l=as.length;i<l;i++){
            as[i].style.background="#fff";
        }
        }

        as[index].style.background="#567";
        as[index+1].style.background="#fff";
        }
        if(event.keyCode==13){            
            title.innerHTML=as[index].innerHTML;
            index=-1;
            menu.style.display="none";                      
        }