<div class="fixed-action-btn show-mobile-only">
  <a class="btn-floating btn-large light-green" title="Back to Top" onclick="scrolltoTop()" id="scrollBtn">
    <i class="material-icons">keyboard_arrow_up</i>
  </a>
</div>

<script>
  // When the user scrolls down 100px from the top of the document, show the button
  window.onscroll = function () { scrollFunction() };

  function scrollFunction() {
    if (document.body.scrollTop > 100 || document.documentElement.scrollTop > 100) {
      document.getElementById("scrollBtn").style.display = "inline-block";
    } else {
      document.getElementById("scrollBtn").style.display = "none";
    }
  }

  // When the user clicks on the button, scroll to the top of the document
  function scrolltoTop() {
    document.body.scrollTop = 0; // For Safari
    document.documentElement.scrollTop = 0; // For Chrome, Firefox, IE and Opera
  }
</script>