gecko-dev/dom/base/test/worker_postMessages.js

function test_workers() {
  onmessage = function(e) {
    postMessage(e.data, e.ports);
  };
}

function test_broadcastChannel() {
  var bc = new BroadcastChannel("postMessagesTest_inWorkers");
  bc.onmessage = function(e) {
    postMessage(e.data);
  };
}

function test_messagePort(port) {
  port.onmessage = function(e) {
    postMessage(e.data, e.ports);
  };
}

onmessage = function(e) {
  if (e.data == "workers") {
    test_workers();
    postMessage("ok");
  } else if (e.data == "broadcastChannel") {
    test_broadcastChannel();
    postMessage("ok");
  } else if (e.data == "messagePort") {
    test_messagePort(e.ports[0]);
    postMessage("ok");
  } else {
    postMessage("ko");
  }
};