// javascript document
function gotopex(){
        var obj=document.getelementbyid("gotopbtn");
        function getscrolltop(){
                return document.documentelement.scrolltop;
            }
        function setscrolltop(value){
                document.documentelement.scrolltop=value;
            }    
        window.onscroll=function(){getscrolltop()>0?obj.style.display="":obj.style.display="none";}
        obj.onclick=function(){
            var gotop=setinterval(scrollmove,10);
            function scrollmove(){
                    setscrolltop(getscrolltop()/1.1);
                    if(getscrolltop()<1)clearinterval(gotop);
                }
        }
    }