https://www.milestonesmuseum.org.uk/modules/custom/spektrix_import/js/spektrix_basket_badge.js?tlvu1i

1(function (Drupal, once) {
2  function parseBasketCount(value) {
3    var count = parseInt(String(value || '').trim(), 10);
4    if (isNaN(count) || count < 0) {
5      return 0;
6    }
7    return count;
8  }
9
10  function syncBasketBadge(badge) {
11    var count = parseBasketCount(badge.textContent);
12    var isEmpty = count <= 0;
13    var lastCount = badge.dataset.basketCount;
14
15    if (lastCount === String(count)) {
16      return;
17    }
18
19    badge.dataset.basketCount = String(count);
20    badge.classList.toggle('is-empty', isEmpty);
21    badge.setAttribute('aria-hidden', isEmpty ? 'true' : 'false');
22  }
23
24  function observeBasketBadge(badge) {
25    syncBasketBadge(badge);
26
27    if (typeof MutationObserver === 'undefined') {
28      return;
29    }
30
31    var scheduled = false;
32    var observer = new MutationObserver(function () {
33      if (scheduled) {
34        return;
35      }
36      scheduled = true;
37      requestAnimationFrame(function () {
38        scheduled = false;
39        syncBasketBadge(badge);
40      });
41    });
42
43    observer.observe(badge, {
44      childList: true,
45      characterData: true,
46      subtree: true
47    });
48  }
49
50  Drupal.behaviors.spektrixBasketBadge = {
51    attach: function (context) {
52      once('spektrix-basket-badge', '.cart-link__badge[data-basket-item-count]', context).forEach(function (badge) {
53        observeBasketBadge(badge);
54      });
55    }
56  };
57})(Drupal, once);