https://www.novasol.co.uk/themes/custom/solar_theme/js/scroll-to-top.js?tk2h7g

1/* global Drupal */
2
3(function () {
4
5  'use strict';
6
7  var aboveBreakpoint = false;
8  var breakpoint = 768;
9  var debounceTimer;
10  var className = 'scroll-to-top';
11  var scrolledState = '--scrolled';
12  var activeState = '--active';
13  var duration = 200;
14
15  var magicNumber = 300; // What is this? Was here since the beginning.
16
17  function getViewport() {
18    var e = window;
19    var a = 'inner';
20
21    if (!('innerWidth' in window)) {
22      a = 'client';
23      e = document.documentElement || document.body;
24    }
25    return {
26      width: e[a + 'Width'],
27      height: e[a + 'Height']
28    };
29  }
30
31  function eachNode(callback, container) {
32    var c = container;
33    if (!c) {
34      c = document;
35    }
36    var nodes = c.querySelectorAll('.' + className);
37    [].forEach.call(nodes, callback);
38  }
39
40  function hide() {
41    eachNode(function (node) {
42      if (!node.classList.contains(className + scrolledState)) {
43        return;
44      }
45      node.classList.remove(className + activeState);
46      setTimeout(function () {
47        node.classList.remove(className + scrolledState);
48      }, duration);
49    });
50  }
51
52  function show() {
53    eachNode(function (node) {
54      if (node.classList.contains(className + scrolledState)) {
55        return;
56      }
57      node.classList.add(className + scrolledState);
58      setTimeout(function () {
59        node.classList.add(className + activeState);
60      }, duration);
61    });
62  }
63
64  function handleScroll() {
65    if (!aboveBreakpoint) {
66      hide();
67      return;
68    }
69    if (document.documentElement.scrollTop <= magicNumber) {
70      hide();
71    } else {
72      show();
73    }
74  }
75
76  function setBreakpointState() {
77    clearTimeout(debounceTimer);
78    debounceTimer = setTimeout(function () {
79      aboveBreakpoint = getViewport().width >= breakpoint;
80      handleScroll();
81    }, 10);
82  }
83
84  function handleClick(e) {
85    window.smoothScroll('#header', 0);
86    e.preventDefault();
87  }
88
89  function attach(context) {
90    eachNode(function (node) {
91      node.removeAttribute('href');
92      node.addEventListener('click', handleClick, true);
93    }, context);
94  }
95
96  window.addEventListener('scroll', handleScroll, true);
97  window.addEventListener('resize', setBreakpointState, true);
98
99  setBreakpointState();
100
101  Drupal.behaviors.scrollToTop = { attach: attach };
102})();
103