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    ServiceWorkerGlobalScope

    by 6 contributors:

    This is an experimental technology
    Because this technology's specification has not stabilized, check the compatibility table for the proper prefixes to use in various browsers. Also note that the syntax and behavior of an experimental technology is subject to change in future versions of browsers as the spec changes.

    The ServiceWorkerGlobalScope interface of the ServiceWorker API represents the global execution context of a service worker.

    Developers should keep in mind that the ServiceWorker.state is not persisted across the termination/restart cycle, so each event handler should assume it's being invoked with a bare, default global state.

    Once successfully registered, a service worker can and will be terminated when idle to conserve memory and processor power. An active service worker is automatically restarted to respond to events, such as ServiceWorkerGlobalScope.onfetch or ServiceWorkerGlobalScope.onmessage.

    Additionally, synchronous requests are not allowed from within a service worker — only asynchronous requests, like those initiated via the fetch() method, can be used.

    This interface inherits from the WorkerGlobalScope interface, and its parent EventTarget, and therefore implements properties from WindowTimers, WindowBase64, and WindowEventHandlers.

    Properties

    ServiceWorkerGlobalScope.clients Read only
    Contains the Clients object associated with the service worker.
    ServiceWorkerGlobalScope.registration Read only
    Contains the ServiceWorkerRegistration object that represents the service worker's registration.
    ServiceWorkerGlobalScope.caches Read only
    Contains the CacheStorage object associated with the service worker.

    Event handlers

    ServiceWorkerGlobalScope.onactivate
    An event handler fired whenever an activate event occurs — when a ServiceWorkerRegistration acquires a new ServiceWorkerRegistration.active worker.
    ServiceWorkerGlobalScope.onbeforeevicted
    Not defined in the spec yet, but it looks like this will be fired when the device is nearly out of storage space, prompting the UA to start claiming back some space from web apps that are using client-side storage, and the current app is targeted.
    ServiceWorkerGlobalScope.onevicted
    Not defined in the spec yet, but it looks like this will be fired when the device is out of storage space, and the UA claims back some space from the current app.
    ServiceWorkerGlobalScope.onfetch
    An event handler fired whenever a fetch event occurs — when a fetch() is called.
    ServiceWorkerGlobalScope.oninstall
    An event handler fired whenever an install event occurs — when a ServiceWorkerRegistration acquires a new ServiceWorkerRegistration.installing worker.
    ServiceWorkerGlobalScope.onmessage
    An event handler fired whenever a message event occurs — when incoming messages are received. Controlled pages can use the MessagePort.postMessage() method to send messages to service workers. The service worker can optionally send a response back via the MessagePort exposed in event.data.port, corresponding to the controlled page.
    ServiceWorkerGlobalScope.onnotificationclick
    An event handler fired whenever a notificationclick event occurs — when a user clicks on a displayed notification.
    ServiceWorkerGlobalScope.onpush
    An event handler fired whenever a push event occurs — when a server push notification is received. 
    ServiceWorkerGlobalScope.onpushsubscriptionchange
    An event handler fired whenever a pushsubscriptionchange event occurs — when a push subscription has been invalidated, or is about to be invalidated (e.g. when a push service sets an expiration time.)

    Methods

    ServiceWorkerGlobalScope.skipWaiting()
    Allows the current service worker registration to progress from waiting to active state while service worker clients are using it.

    ServiceWorkerGlobalScope implements WorkerGlobalScope — which implements GlobalFetch. Therefore it also has the following property available to it:

    GlobalFetch.fetch()
    Starts the process of fetching a resource. This returns a promise that resolves to the Response object representing the Response to your request. This algorithm is the entry point for the fetch handling handed to the service worker context.

    Examples

    This code snippet is from the service worker prefetch sample (see prefetch example live.) The ServiceWorkerGlobalScope.onfetch event handler listens for the fetch event. When fired, the code returns a promise that resolves to the first matching request in the Cache object. If no match is found, the code fetches a response from the network.

    The code also handles exceptions thrown from the fetch() operation. Note that an HTTP error response (e.g., 404) will not trigger an exception. It will return a normal response object that has the appropriate error code set.

    self.addEventListener('fetch', function(event) {
  console.log('Handling fetch event for', event.request.url);

  event.respondWith(
    caches.match(event.request).then(function(response) {
      if (response) {
        console.log('Found response in cache:', response);

        return response;
      }
      console.log('No response found in cache. About to fetch from network...');

      return fetch(event.request).then(function(response) {
        console.log('Response from network is:', response);

        return response;
      }).catch(function(error) {
        console.error('Fetching failed:', error);

        throw error;
      });
    })
  );
});

    Specifications

    Specification Status Comment
    Service Workers
    The definition of 'ServiceWorkerGlobalScope' in that specification.    		 Working Draft Initial definition.
    Fetch
    The definition of 'Fetch' in that specification.    		 Living Standard Adds the fetch method.
    Push API
    The definition of 'onpush' in that specification.    		 Working Draft Adds the
    onpush and onpushsubscriptionchange event handlers.
    Notifications API
    The definition of 'onnotificationclick' in that specification.    		 Living Standard Adds the onnotificationclick event handler.

    Browser compatibility

    Feature Chrome Firefox (Gecko) Internet Explorer Opera Safari (WebKit)
    Basic support 40.0 33.0 (33.0) Not supported 24 Not supported
    onnotificationclick (Yes) 42.0 (42.0) Not supported (Yes) Not supported
    Feature Android Firefox Mobile (Gecko) Firefox OS IE Mobile Opera Mobile Safari Mobile Chrome for Android
    Basic support ? ? (Yes) Not supported ? Not supported ?
    onnotificationclick ? 42.0 (42.0) (Yes) Not supported ? Not supported ?

    See also

    Document Tags and Contributors

    Tags: 
    Contributors to this page: Speculative, chrisdavidmills, jpmedley, teoli, fscholz, Meggin
    Last updated by: Speculative,