https://kamurria.com/assets/js/scroll_totop_button.js

1//Scroll back to top
2
3(function($) { "use strict";
4
5    $(document).ready(function(){"use strict";
6
7        var progressPath = document.querySelector('.progress-wrap path');
8        var pathLength = progressPath.getTotalLength();
9        progressPath.style.transition = progressPath.style.WebkitTransition = 'none';
10        progressPath.style.strokeDasharray = pathLength + ' ' + pathLength;
11        progressPath.style.strokeDashoffset = pathLength;
12        progressPath.getBoundingClientRect();
13        progressPath.style.transition = progressPath.style.WebkitTransition = 'stroke-dashoffset 10ms linear';
14        var updateProgress = function () {
15            var scroll = $(window).scrollTop();
16            var height = $(document).height() - $(window).height();
17            var progress = pathLength - (scroll * pathLength / height);
18            progressPath.style.strokeDashoffset = progress;
19        }
20        updateProgress();
21        $(window).scroll(updateProgress);
22        var offset = 50;
23        var duration = 550;
24        jQuery(window).on('scroll', function() {
25            if (jQuery(this).scrollTop() > offset) {
26                jQuery('.progress-wrap').addClass('active-progress');
27            } else {
28                jQuery('.progress-wrap').removeClass('active-progress');
29            }
30        });
31        jQuery('.progress-wrap').on('click', function(event) {
32            event.preventDefault();
33            jQuery('html, body').animate({scrollTop: 0}, duration);
34            return false;
35        })
36
37
38    });
39
40})(jQuery);