denoland-deno/cli/tests/subdir/nested_worker.js

// Specifier should be resolved relative to current file
const jsWorker = new Worker("./sibling_worker.js", {
  type: "module",
  name: "sibling"
});

jsWorker.onerror = _e => {
  postMessage({ type: "error" });
};

jsWorker.onmessage = e => {
  console.log("js worker on message");
  postMessage({ type: "msg", text: e });
  close();
};

onmessage = function(e) {
  jsWorker.postMessage(e.data);
};