Bootstrap 5 Cookie Consent Banner for Vanilla JS

<!-- Requires Bootstrap 5.3 CSS + theme.css:
<link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/bootstrap@5.3.3/dist/css/bootstrap.min.css">
<link rel="stylesheet" href="theme.css"> -->
<div>
  <div data-show="banner">
    <div class="position-fixed start-0 end-0 bottom-0 z-3 p-3" role="region" aria-label="Cookie consent">
      <div class="mw-4xl mx-auto p-4 bg-body border shadow-sm rounded-3">
        <h2 class="fs-5 fw-semibold text-body-emphasis">We value your privacy</h2>
        <p class="mt-2 small text-body-secondary">We use essential cookies to run this site. With your permission we also use analytics and marketing cookies. You can change your choice at any time. <a href="#" class="text-brand fw-medium text-decoration-none">Cookie policy</a></p>
        <div data-show="prefs" hidden>
          <div class="mt-3 d-flex flex-column gap-2">
            <label class="d-flex align-items-start gap-2 small text-body">
              <input type="checkbox" class="form-check-input mt-0 mt-1" checked disabled>
              <span><strong>Strictly necessary</strong> — security, load balancing, your consent choice. Always on.</span>
            </label>
            <label class="d-flex align-items-start gap-2 small text-body">
              <input id="cc-analytics" type="checkbox" class="form-check-input mt-0 mt-1">
              <span><strong>Analytics</strong> — anonymous usage statistics that help us improve.</span>
            </label>
            <label class="d-flex align-items-start gap-2 small text-body">
              <input id="cc-marketing" type="checkbox" class="form-check-input mt-0 mt-1">
              <span><strong>Marketing</strong> — personalised ads and campaign measurement.</span>
            </label>
          </div>
        </div>
        <div class="mt-3 d-flex flex-wrap align-items-center gap-2">
          <button type="button" class="btn btn-brand fw-semibold rounded-2" data-call="rejectAll" data-close="banner">Reject all</button>
          <button type="button" class="btn btn-brand fw-semibold rounded-2" data-call="acceptAll" data-close="banner">Accept all</button>
          <button type="button" class="btn btn-link link-body-emphasis text-decoration-none fw-semibold rounded-2" data-toggle="prefs" data-expanded="prefs" aria-expanded="false">Customize</button>
          <div data-show="prefs" hidden>
            <button type="button" class="btn btn-outline-secondary fw-semibold rounded-2" data-call="savePreferences" data-close="banner">Save preferences</button>
          </div>
        </div>
      </div>
    </div>
  </div>
  <div data-hide="banner" hidden>
    <button type="button" class="position-fixed bottom-0 start-0 m-3 btn btn-outline-secondary fw-semibold rounded-2" data-open="banner">Cookie settings</button>
  </div>
</div>

<script>
  (() => {
    const CONSENT_KEY = 'cookie-consent-v1'; // bump the version to re-ask after policy changes

    function readConsent() {
      try {
        return JSON.parse(localStorage.getItem(CONSENT_KEY));
      } catch {
        return null; // storage blocked / SSR → treat as "not decided"
      }
    }

    function saveConsent(choice) {
      const record = { necessary: true, ...choice, timestamp: new Date().toISOString() };
      try {
        localStorage.setItem(CONSENT_KEY, JSON.stringify(record));
      } catch {}
      // Google Consent Mode v2: only grant what the user chose.
      window.gtag?.('consent', 'update', {
        analytics_storage: choice.analytics ? 'granted' : 'denied',
        ad_storage: choice.marketing ? 'granted' : 'denied',
        ad_user_data: choice.marketing ? 'granted' : 'denied',
        ad_personalization: choice.marketing ? 'granted' : 'denied'
      });
      // Load optional scripts by listening for this event.
      document.dispatchEvent(new CustomEvent('cookie-consent', { detail: record }));
    }

    function acceptAll() {
      saveConsent({ analytics: true, marketing: true });
    }

    function rejectAll() {
      saveConsent({ analytics: false, marketing: false });
    }

    function savePreferences() {
      saveConsent({
        analytics: Boolean(document.getElementById('cc-analytics')?.checked),
        marketing: Boolean(document.getElementById('cc-marketing')?.checked)
      });
    }
    const state = { banner: !readConsent(), prefs: false };
    const actions = { acceptAll, rejectAll, savePreferences };
    const pair = (s) => s.split(':');
    const sync = () => {
      document.querySelectorAll('[data-show]').forEach((el) => (el.hidden = !state[el.dataset.show]));
      document.querySelectorAll('[data-hide]').forEach((el) => (el.hidden = !!state[el.dataset.hide]));
      document.querySelectorAll('[data-when]').forEach((el) => { const [k, v] = pair(el.dataset.when); el.hidden = state[k] !== v; });
      document.querySelectorAll('[data-pressed]').forEach((el) => { const [k, v] = pair(el.dataset.pressed); el.setAttribute('aria-pressed', String(state[k] === v)); });
      document.querySelectorAll('[data-expanded]').forEach((el) => el.setAttribute('aria-expanded', String(!!state[el.dataset.expanded])));
    };
    document.addEventListener('click', (e) => {
      const t = e.target.closest('[data-toggle],[data-open],[data-close],[data-set],[data-call]');
      if (!t) return;
      const { toggle, open, close, set, call } = t.dataset;
      if (call) actions[call]?.(e);
      if (toggle) state[toggle] = !state[toggle];
      if (open) state[open] = true;
      if (close) state[close] = false;
      if (set) { const [k, v] = pair(set); state[k] = v; }
      sync();
    });
    sync();
  })();
</script>

/* theme.css — brand color #4f46e5 for Bootstrap 5.3 */
:root { --brand: #4f46e5; --brand-hover: #433cc3; --brand-rgb: 79, 70, 229; --brand-contrast: #ffffff; }
.btn-brand {
  --bs-btn-color: var(--brand-contrast); --bs-btn-bg: var(--brand); --bs-btn-border-color: var(--brand);
  --bs-btn-hover-color: var(--brand-contrast); --bs-btn-hover-bg: var(--brand-hover); --bs-btn-hover-border-color: var(--brand-hover);
  --bs-btn-active-color: var(--brand-contrast); --bs-btn-active-bg: var(--brand-hover); --bs-btn-active-border-color: var(--brand-hover);
  --bs-btn-focus-shadow-rgb: var(--brand-rgb);
}
.text-brand { color: var(--brand) !important; }
.border-brand { border: 2px solid var(--brand) !important; }
.bg-brand-subtle { background-color: rgba(var(--brand-rgb), .12) !important; }
.form-control:focus, .form-check-input:focus { border-color: var(--brand); box-shadow: 0 0 0 .25rem rgba(var(--brand-rgb), .25); }
.form-check-input:checked { background-color: var(--brand); border-color: var(--brand); }
.overlay { background: rgba(15, 23, 42, .5); backdrop-filter: blur(4px); z-index: 1050; }
.choice[aria-pressed="true"] { border-color: var(--brand) !important; color: var(--brand) !important; box-shadow: 0 0 0 .2rem rgba(var(--brand-rgb), .2); }
.mw-sm { max-width: 24rem; } .mw-md { max-width: 28rem; } .mw-lg { max-width: 32rem; } .mw-xl { max-width: 36rem; }
.mw-2xl { max-width: 42rem; } .mw-4xl { max-width: 56rem; } .mw-6xl { max-width: 72rem; }