WakeLockSentinel.released
  The read-only released property of the
  WakeLockSentinel interface returns a boolean that indicates whether
  a WakeLockSentinel has been released yet.
Syntax
var released = sentinel.released;
Value
  A boolean value, that is false until the
  WakeLockSentinel has been released (either through a call to
  WakeLockSentinel.release() or because the lock has been released
  automatically) and the release event has been
  emitted, after which it becomes true and no longer changes.
Examples
  This example shows how released's value changes within a
  WakeLockSentinel's life cycle.
const sentinel = await navigator.wakeLock.request('screen');
console.log(sentinel.released);  // Logs "false"
sentinel.onrelease = () => {
  console.log(sentinel.released);  // Logs "true"
};
await sentinel.release();
Specifications
| Specification | 
|---|
| Screen Wake Lock API  # dom-wakelocksentinel-released  | 
Browser compatibility
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