https://americansongwriter.com/wp-content/themes/bimber/js/back-to-top.js?m=1764838929g

1(function ($) {
2
3    'use strict';
4
5    g1.backToTop = function () {
6        var $scrollToTop = $('.g1-back-to-top');
7
8        // init
9        toggleVisibility($scrollToTop);
10
11        $scrollToTop.on('click', function (e) {
12            e.preventDefault();
13
14            var multipier = 200;
15            var durationRange = {
16                min: 200,
17                max: 1000
18            };
19
20            var winHeight = $(window).height();
21            var docHeight = $(document).height();
22            var proportion = Math.floor(docHeight / winHeight);
23
24            var duration = proportion * multipier;
25
26            if (duration < durationRange.min) {
27                duration = durationRange.min;
28            }
29
30            if (duration > durationRange.max) {
31                duration = durationRange.max;
32            }
33
34            $('html, body').animate({
35                scrollTop: 0
36            }, duration);
37        });
38
39        $(window).scroll(function() {
40            window.requestAnimationFrame(function () {
41                toggleVisibility($scrollToTop);
42            });
43        });
44    };
45
46    function toggleVisibility ($scrollToTop) {
47        if ($(window).scrollTop() > 240) {
48            $scrollToTop.addClass('g1-back-to-top-on').removeClass('g1-back-to-top-off');
49        } else {
50            $scrollToTop.addClass('g1-back-to-top-off').removeClass('g1-back-to-top-on');
51        }
52    }
53
54    $(document).ready(function () {
55        g1.backToTop();
56    });
57})(jQuery);
58