回到顶部实现

这是顶部
<!--<a href="javaScript:;" id="back" onclick="goback()">goback!</a>
<a href="javaScript:void(0);" id="back" onclick="goback()">goback!</a>-->

<a href="javaScript:;" id="back" onclick="goback()">goback!</a>

body{
  height: 2000px;
}
#back{
  position: fixed;
  bottom: 0px;
  right: 0px;
  width: 50px;
  height: 50px;
  background: red;
}

function goback(){
  //scrollTo(0,0);

  //var iScrollTop = document.body.scrollTop; //360,Chrome,
  //var iScrollTop = document.documentElement.scrollTop;  //IE8,火狐
  var iScrollTop = document.body.scrollTop || document.documentElement.scrollTop;
  //alert(iScrollTop);

  var timer = setInterval(function(){  //定时器
    scrollTo(0,iScrollTop-=100);
    console.log(iScrollTop);
    if(iScrollTop <= 0){
      clearInterval(timer);  //清除定时器
    }
  },100);
  return false;
}