Vielzeug

Prevent Screen Sleep ​

Problem ​

A long-running interactive session: a game, timer, or presentation: should keep the screen awake, but the Screen Wake Lock API auto-releases when the tab is hidden and must be re-requested on return. Managing that lifecycle by hand is error-prone.

Solution ​

Use createWakeLock() to acquire the lock once; the Sentinel re-acquires it automatically after visibility changes.

ts
import { createWakeLock } from '@vielzeug/sentinel';

const wakeLock = createWakeLock();

// Acquire when the active session starts
wakeLock.request();

const unsubscribe = wakeLock.subscribe(() => {
  console.log('Wake lock active:', wakeLock.getSnapshot().active);
});

// Release when the session ends
wakeLock.release();
unsubscribe();
wakeLock.dispose();

Pitfalls ​

  • The Wake Lock API requires a secure context (HTTPS or localhost); it is silently unavailable in non-secure environments.
  • The OS may deny or cancel the lock when battery is critically low.
  • request() is best-effort: check getSnapshot().supported if your UI should adapt to unsupported browsers.