web-locks/resources/sw-controlled-iframe.html

<!DOCTYPE html>
<meta charset=utf-8>
<title>iframe used in clientId test</title>
<script>

self.onmessage = async event => {
  try {
    if (event.data === 'get_sw_client_id') {
      // Use the controlling service worker to determine
      // this client's id according to the Service Worker.
      const response = await fetch('/clientId');
      const data = await response.json();
      window.parent.postMessage(data.clientId, '*');
      return;
    }

    if (event.data === 'get_lock_client_id') {
      // Grab a lock, then query the lock manager for state to
      // determine this client's id according to the lock manager.
      await navigator.locks.request('lock-name', async lock => {
        const lock_state = await navigator.locks.query();
        const held_lock = lock_state.held.filter(l => l.name === lock.name)[0];
        window.parent.postMessage(held_lock.clientId, '*');
      });
      return;
    }

    window.parent.postMessage(`unknown request: ${event.data}`, '*');
  } catch (ex) {
    // In case of test failure, don't leave parent window hanging.
    window.parent.postMessage(`${ex.name}: ${ex.message}`, '*');
  }
};

</script>