chrome/test/data/workers/fetch_from_worker.html

<script>
const params = new URLSearchParams(location.search);
const worker = new Worker(params.get('script'));
worker.onmessage = e => {
  document.body.innerText += e.data;
  document.title = 'DONE';
};

function fetch_from_worker(url) {
  document.title = 'Fetching';
  document.body.innerText = '';
  worker.postMessage({url: url});
}
</script>