Scroll To Top Jquery Function and html

<script>

$(window).scroll(function() {
    if ($(window).scrollTop() > 100) {
        // > 100px from top - show div
      $('.scrollBtn').show();

    }
    else {
        // <= 100px from top - hide div
      $('.scrollBtn').hide();
    }
});

$("#button").click(function() {
   $('html, body').animate({
        scrollTop: $("header").offset().top
    }, 2000);
});$

</script>

<div class="scrollBtn" style="display: none;"> <
a href="javascript:;" id="scrollButton"><img src="images/arrowUp.png"></a>
</div>

<style>
.scrollBtn {
position: fixed; 
right: 20px; 
bottom: 20px; 
width: 40px; 
height: 40px; 
z-index: 10;}
.scrollBtn img {width: 100%; }
</style>