denoland-deno/cli/tests/026_workers.ts

const jsWorker = new Worker("./subdir/test_worker.js", { type: "module" });
const tsWorker = new Worker("./subdir/test_worker.ts", { type: "module" });

tsWorker.onmessage = (e): void => {
  console.log("Received ts: " + e.data);
};

jsWorker.onmessage = (e): void => {
  console.log("Received js: " + e.data);

  tsWorker.postMessage("Hello World");
};

jsWorker.onerror = (e: Event): void => {
  e.preventDefault();
  console.log("called onerror in script");
  jsWorker.postMessage("Hello World");
};

jsWorker.postMessage("Hello World");