https://www.elle.cz/js/modules/gallery/galleryHash.js

1export function replaceGalleryHash(index) {
2  const url = new URL(window.location.href);
3  const newHash = `#fotka-${index + 1}`;
4
5  if (url.hash !== newHash) {
6    url.hash = newHash;
7    window.history.replaceState(null, '', url);
8  }
9}
10
11export function getGalleryIndexFromHash(slideCount) {
12  const match = window.location.hash.match(/^#fotka-(\d+)$/);
13  if (!match) {
14    return null;
15  }
16
17  const photoNumber = Number.parseInt(match[1], 10);
18  const index = photoNumber - 1;
19
20  return index >= 0 && index < slideCount ? index : null;
21}