https://willmering.de/fileadmin/CI/js/styleswitcher.js

1function setActiveStyleSheet(title) {
2  var i, a, main;
3  for(i=0; (a = document.getElementsByTagName("link")[i]); i++) {
4    if(a.getAttribute("rel").indexOf("style") != -1 && a.getAttribute("title")) {
5      a.disabled = true;
6      if(a.getAttribute("title") == title) a.disabled = false;
7    }
8  }
9}
10
11function getActiveStyleSheet() {
12  var i, a;
13  for(i=0; (a = document.getElementsByTagName("link")[i]); i++) {
14    if(a.getAttribute("rel").indexOf("style") != -1 && a.getAttribute("title") && !a.disabled) return a.getAttribute("title");
15  }
16  return null;
17}
18
19function getPreferredStyleSheet() {
20  var i, a;
21  for(i=0; (a = document.getElementsByTagName("link")[i]); i++) {
22    if(a.getAttribute("rel").indexOf("style") != -1
23       && a.getAttribute("rel").indexOf("alt") == -1
24       && a.getAttribute("title")
25       ) return a.getAttribute("title");
26  }
27  return null;
28}
29
30function createCookie(name,value,days) {
31  if (days) {
32    var date = new Date();
33    date.setTime(date.getTime()+(days*24*60*60*1000));
34    var expires = "; expires="+date.toGMTString();
35  }
36  else expires = "";
37  document.cookie = name+"="+value+expires+"; path=/";
38}
39
40function readCookie(name) {
41  var nameEQ = name + "=";
42  var ca = document.cookie.split(';');
43  for(var i=0;i < ca.length;i++) {
44    var c = ca[i];
45    while (c.charAt(0)==' ') c = c.substring(1,c.length);
46    if (c.indexOf(nameEQ) == 0) return c.substring(nameEQ.length,c.length);
47  }
48  return null;
49}
50
51window.onload = function(e) {
52  var cookie = readCookie("style");
53  var title = cookie ? cookie : getPreferredStyleSheet();
54  setActiveStyleSheet(title);
55}
56
57window.onunload = function(e) {
58  var title = getActiveStyleSheet();
59  createCookie("style", title, 365);
60}
61
62var cookie = readCookie("style");
63var title = cookie ? cookie : getPreferredStyleSheet();
64setActiveStyleSheet(title);