// main.js
const { RemoteReadableStream, RemoteWritableStream } = RemoteWebStreams;
(async () => {
  const worker = new Worker('./worker.js');
  // create a stream to send the input to the worker
  const { writable, readablePort } = new RemoteWritableStream();
  // create a stream to receive the output from the worker
  const { readable, writablePort } = new RemoteReadableStream();
  // transfer the other ends to the worker
  worker.postMessage({ readablePort, writablePort }, [readablePort, writablePort]);

  const response = await fetch('./some-data.txt');
  await response.body
    // send the downloaded data to the worker
    // and receive the results back
    .pipeThrough({ readable, writable })
    // show the results as they come in
    .pipeTo(new WritableStream({
      write(chunk) {
        const results = document.getElementById('results');
        results.appendChild(document.createTextNode(chunk)); // tadaa!
      }
    }));
})();

// worker.js
const { fromReadablePort, fromWritablePort } = RemoteWebStreams;
self.onmessage = async (event) => {
  // create the input and output streams from the transferred ports
  const { readablePort, writablePort } = event.data;
  const readable = fromReadablePort(readablePort);
  const writable = fromWritablePort(writablePort);

  // process data
  await readable
    .pipeThrough(new TransformStream({
      transform(chunk, controller) {
        controller.enqueue(process(chunk)); // do the actual work
      }
    }))
    .pipeTo(writable); // send the results back to main thread
};