ServiceWorkerContainer

The ServiceWorkerContainer interface of the ServiceWorker API provides an object representing the service worker as an overall unit in the network ecosystem, including facilities to register, unregister and update service workers, and access the state of service workers and their registrations.

Most importantly, it exposes the ServiceWorkerContainer.register() method used to register service workers, and the ServiceWorkerContainer.controller property used to determine whether or not the current page is actively controlled.

Properties

ServiceWorkerContainer.controller Read only

Returns a ServiceWorker object if its state is activated (the same object returned by ServiceWorkerRegistration.active). This property returns null during a force-refresh request (Shift + refresh) or if there is no active worker.

ServiceWorkerContainer.ready Read only

Provides a way of delaying code execution until a service worker is active. It returns a Promise that will never reject, and which waits indefinitely until the ServiceWorkerRegistration associated with the current page has an ServiceWorkerRegistration.active worker. Once that condition is met, it resolves with the ServiceWorkerRegistration.

Event handlers

ServiceWorkerContainer.oncontrollerchange

Fired whenever a controllerchange event occurs — when the document's associated ServiceWorkerRegistration acquires a new active worker.

ServiceWorkerContainer.onerror

Fired whenever an error event occurs in the associated service workers.

ServiceWorkerContainer.onmessage

Fired whenever a message event occurs — when incoming messages are received to the ServiceWorkerContainer object (e.g. via a MessagePort.postMessage() call.)

Methods

ServiceWorkerContainer.register()

Creates or updates a ServiceWorkerRegistration for the given scriptURL.

ServiceWorkerContainer.getRegistration()

Gets a ServiceWorkerRegistration object whose scope matches the provided document URL. If the method can't return a ServiceWorkerRegistration, it returns a Promise.

ServiceWorkerContainer.getRegistrations()

Returns all ServiceWorkerRegistration objects associated with a ServiceWorkerContainer in an array. If the method can't return ServiceWorkerRegistration objects, it returns a Promise.

ServiceWorkerContainer.startMessages()

Explicitly starts the flow of messages being dispatched from a service worker to pages under its control (e.g. sent via Client.postMessage()). Can be used to avoid race conditions created when a service worker tries to post a message to a page before that page has actually finished loading an ServiceWorkerContainer.onmessage handler to process them.

Examples

The example below first checks to see if the browser supports service workers. If supported, the code registers the service worker and determines if the page is actively controlled by the service worker. If it isn't, it prompts the user to reload the page so the service worker can take control. The code also reports any registration failures.

if ('serviceWorker' in navigator) {
  // Register a service worker hosted at the root of the
  // site using the default scope.
  navigator.serviceWorker.register('/sw.js').then(function(registration) {
    console.log('Service worker registration succeeded:', registration);

    // At this point, you can optionally do something 
    // with registration. See https://developer.mozilla.org/en-US/docs/Web/API/ServiceWorkerRegistration
  }).catch(function(error) {
    console.log('Service worker registration failed:', error);
  });

  // Independent of the registration, let's also display
  // information about whether the current page is controlled
  // by an existing service worker, and when that
  // controller changes.

  // First, do a one-off check if there's currently a
  // service worker in control.
  if (navigator.serviceWorker.controller) {
    console.log('This page is currently controlled by:', navigator.serviceWorker.controller);
  }

  // Then, register a handler to detect when a new or
  // updated service worker takes control.
  navigator.serviceWorker.oncontrollerchange = function() {
    console.log('This page is now controlled by:', navigator.serviceWorker.controller);
  };
} else {
  console.log('Service workers are not supported.');
}

Specifications

Browser compatibilityUpdate compatibility data on GitHub

See also

• Using Service Workers
• Service workers basic code example
• Is ServiceWorker ready?
• Promise
• Using web workers