预览地址 https://emloxe.github.io/xydaily-component/other/backtop.html 

代码地址 https://github.com/emloxe/xydaily-component/blob/master/other/backtop.html 

 

<a class="to-top"> </a>
<script src="./jquery.toTop.min.js"></script>
<script>
$(function() {
  $('.to-top').toTop();
});
</script>