How to Add Back to Top Button by following below steps:
1. Create new snippet by following below instructions.
- Find the theme you want to edit, and then click Actions > Edit code.
- In the Snippets directory, click Add a new snippet.
- Name your snippet back-to-the-top, then click Create snippet. Your snippet file opens in the code editor.
- Paste the following code into your newly created back-to-the-top file:
2. Paste below code in the snipped back-to-top
{% comment %}
Reduce below value if you need the back to the top button to appear higher up on the page.
That value is in pixels.
{% endcomment %}
{% assign vertical_offset_for_trigger = 300 %}
{% comment %}
Vertical offset from bottom of browser for the position of the button.
{% endcomment %}
{% assign position_from_bottom = '6em' %}
<a id="BackToTop" href="#" title="Back to the top" class="back-to-top hide"> <i class="fa fa-arrow-circle-o-up fa-2x"></i>
</a>
{{ '//netdna.bootstrapcdn.com/font-awesome/4.0.3/css/font-awesome.min.css' | stylesheet_tag }}
<style>
.back-to-top {
position: fixed;
bottom: {{ position_from_bottom }};
right: 0px;
text-decoration: none;
color: #999;
background-color: #eee;
font-size: 16px;
padding: 0.3em;
-webkit-border-top-left-radius: 3px;
-webkit-border-bottom-left-radius: 3px;
-moz-border-radius-topleft: 3px;
-moz-border-radius-bottomleft: 3px;
border-top-left-radius: 3px;
border-bottom-left-radius: 3px;
z-index: 60000;
}
.back-to-top i {
vertical-align: middle;
}
.back-to-top span {
padding-left: 0.5em;
}
.back-to-top i + span {
padding-left: 0;
}
.back-to-top:hover {
text-decoration: none;
color: #555;
}
.hide {
display: none!important;
}
</style>
<script>
(function() {
function trackScroll() {
var scrolled = window.pageYOffset;
var coords = {{ vertical_offset_for_trigger }};
if (scrolled > coords) {
goTopBtn.classList.remove('hide');
}
if (scrolled < coords) {
goTopBtn.classList.add('hide');
}
}
function backToTop() {
if (window.pageYOffset > 0) {
window.scrollBy(0, -80);
setTimeout(backToTop, 0);
}
}
var goTopBtn = document.querySelector('.back-to-top');
window.addEventListener('scroll', trackScroll);
goTopBtn.addEventListener('click', backToTop);
})();
</script> 
