https://www.samirkhaki.com/assets/js/favicon-switcher.js

1;(function(mod){
2function collectLinks() {
3  return Array.prototype.slice.apply(
4    document.head.querySelectorAll('link[rel*="icon"]')
5  )
6}
7
8function applyLink(source, target) {
9  target.setAttribute('type', source.getAttribute('type'))
10  target.setAttribute('href', source.getAttribute('href'))
11}
12
13// eslint-disable-next-line no-unused-vars
14function initSwitcher(delay) {
15  // Exit if media queries aren't supported
16  if (typeof window.matchMedia !== 'function') {
17    return function noop() {}
18  }
19
20  var links = collectLinks()
21  var current = document.createElement('link')
22  var prevMatch
23
24  current.setAttribute('rel', 'shortcut icon')
25  document.head.appendChild(current)
26
27  function faviconApplyLoop() {
28    var matched
29
30    links.forEach(function(link) {
31      if (window.matchMedia(link.media).matches) {
32        matched = link
33      }
34    })
35
36    if (! matched) {
37      return
38    }
39
40    if (matched.media !== prevMatch) {
41      prevMatch = matched.media
42      applyLink(matched, current)
43    }
44  }
45
46  var intervalId = setInterval(faviconApplyLoop, delay || 300)
47
48  function unsubscribe() {
49    clearInterval(intervalId)
50    links.forEach(function(link) {
51      document.head.appendChild(link)
52    })
53  }
54
55  faviconApplyLoop()
56  links.forEach(function(link) {
57    document.head.removeChild(link)
58  })
59
60  return unsubscribe
61}
62
63initSwitcher()
64})()