let myWorker = new Worker("file_spawn_worker.js");
myWorker.onmessage = function(event) {
  parent.postMessage({
    result: "worker-allowed",
    href: document.location.href,
  }, "*");
}
myWorker.onerror = function(event) {
  parent.postMessage({
    result: "worker-blocked",
    href: document.location.href,
  }, "*");
}

// --------------------------------------------

var mySharedWorker = new SharedWorker('file_spawn_shared_worker.js');
mySharedWorker.port.onmessage = function(ev) {
  parent.postMessage({
    result: "shared-worker-allowed",
    href: document.location.href,
  }, "*");
}
mySharedWorker.onerror = function(evt) {
  evt.preventDefault();
  parent.postMessage({
    result: "shared-worker-blocked",
    href: document.location.href,
  }, "*");
}
mySharedWorker.port.start();
mySharedWorker.port.postMessage('foo');

// --------------------------------------------

navigator.serviceWorker.register('file_spawn_service_worker.js')
.then(function(reg) {
  // registration worked
    reg.unregister().then(function() {
      parent.postMessage({
        result: "service-worker-allowed",
        href: document.location.href,
      }, "*");
    });
}).catch(function(error) {
  // registration failed
  parent.postMessage({
    result: "service-worker-blocked",
    href: document.location.href,
  }, "*");
});