How to Implement mccDeliveryCountdown for Accurate ETAs

Troubleshooting Common mccDeliveryCountdown Issues

1. Countdown not starting

• Cause: Initialization code runs before DOM or required resources are ready.
• Fix: Ensure initialization runs after DOMContentLoaded or in a mounted hook. Example:

document.addEventListener(‘DOMContentLoaded’, () => { mccDeliveryCountdown.init({…});});

2. Timer shows incorrect remaining time

• Cause: Timezone or server-client time mismatch, or wrong end timestamp format.
• Fix: Use UTC timestamps and compute deltas on the client:

const endTs = Date.parse(‘2026-05-20T15:00:00Z’); // UTC ISO 8601const now = Date.now();const remaining = Math.max(0, endTs - now);

Also verify the API returns ISO 8601 or epoch milliseconds as documented.

3. Timer jumps or skips seconds

• Cause: Using setInterval with heavy UI work, repeated re-renders, or relying on Date objects updated incorrectly.
• Fix: Use requestAnimationFrame or compute remaining from absolute timestamps each tick; throttle DOM updates:

function tick(endTs){ const remaining = Math.max(0, endTs - Date.now()); updateDisplay(remaining); if (remaining > 0) requestAnimationFrame(() => tick(endTs));}

4. Multiple timers on the same page conflict

• Cause: Global state or non-scoped event listeners/interval IDs.
• Fix: Encapsulate each countdown instance in a class or factory and keep instance-specific IDs:

class DeliveryCountdown { constructor(endTs, el){ this.endTs = endTs; this.el = el; this.raf = null; } start(){ this.tick(); } tick(){ /compute, update, set raf */ } stop(){ cancelAnimationFrame(this.raf); }}

5. Formatting or localization issues

• Cause: Hardcoded labels, incorrect pluralization, or locale-unaware formatting.
• Fix: Use Intl APIs and provide i18n strings:

const days = Math.floor(ms / 86400000);const formatter = new Intl.RelativeTimeFormat(‘en’, {numeric: ‘auto’});// or format numeric parts manually and localize labels

6. Performance degradation on mobile

• Cause: Frequent DOM updates, heavy animations, or running many intervals.
• Fix: Reduce update frequency to once per second, avoid layout-thrashing, and pause timers when page is hidden:

document.addEventListener(‘visibilitychange’, () => { if (document.hidden) countdown.stop(); else countdown.start();});

7. End-of-countdown behavior not firing

• Cause: Relying on exact millisecond match or not checking for <= 0.
• Fix: Trigger end action when remaining <= 0 and ensure it runs once:

if (remaining <= 0 && !this.ended){ this.ended = true; onComplete(); }

8. Animations out of sync with timer

• Cause: CSS animations not tied to clock or using transition delays.
• Fix: Drive animations from JS state or use CSS variables updated each tick for smooth sync.

9. Accessibility problems

• Cause: Dynamic updates not announced to assistive tech; poor focus management.
• Fix: Provide ARIA live region and accessible labels:

Delivery in 10 minutes

Update that region text on each visible change and avoid excessive announcements.

10. Integration issues with frameworks (React/Vue/Angular)

• Cause: Conflicts between framework reactivity and external timers; memory leaks on unmount.
• Fix: Hook into lifecycle methods to