Scroll to top on Javascript without Jquery | Скролл наверх без Jquery

<style type="text/css" media="all">
#toTop { width:70px;background:#F4FFBF;border:1px solid #ccc;text-align:center;padding:5px;position:fixed;bottom:10px;right:10px;cursor:pointer;color:#666;text-decoration:none; }
</style>
<script type="text/javascript">
var stepTime = 20;
var docBody = document.body;
var focElem = document.documentElement;
var scrollAnimationStep = function (initPos, stepAmount) {
    var newPos = initPos - stepAmount > 0 ? initPos - stepAmount : 0;
    docBody.scrollTop = focElem.scrollTop = newPos;
    newPos && setTimeout(function () {
        scrollAnimationStep(newPos, stepAmount);
    }, stepTime);
}
var scrollTopAnimated = function (speed) {
    var topOffset = docBody.scrollTop || focElem.scrollTop;
    var stepAmount = topOffset;
    speed && (stepAmount = (topOffset * stepTime)/speed);
    scrollAnimationStep(topOffset, stepAmount);
};
</script>
<button id="toTop" onclick="scrollTopAnimated(1000)">Scroll Top</button>

for fast go to top

<a href="javascript:scroll(0,0)">Top</a>