<!DOCTYPE html>
<html>
<script>

// Return a URL of a client when it's successful.
function createAndFetchFromBlobWorker() {
  const fetchURL = new URL('get-worker-client-url.txt', window.location).href;
  const workerScript =
    `self.onmessage = async (e) => {
      const response = await fetch(e.data.url);
      const text = await response.text();
      self.postMessage({"result": text, "expected": self.location.href});
    };`;
  const blob = new Blob([workerScript], { type: 'text/javascript' });
  const blobUrl = URL.createObjectURL(blob);

  const worker = new Worker(blobUrl);
  return new Promise((resolve, reject) => {
    worker.onmessage = e => resolve(e.data);
    worker.onerror = e => reject(e.message);
    worker.postMessage({"url": fetchURL});
  });
}

</script>
</html>