ServiceWorkerGlobalScope

The ServiceWorkerGlobalScope interface of the Service Worker 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 fetch or message.

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.

Instance properties

This interface inherits properties from the WorkerGlobalScope interface, and its parent EventTarget.

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.

Instance properties inherited from WorkerGlobalScope

ServiceWorkerGlobalScope.caches Read only: Returns the CacheStorage object associated with the current context. This object enables functionality such as storing assets for offline use, and generating custom responses to requests.
ServiceWorkerGlobalScope.console Read only Non-standard: Returns the console associated with the worker.
ServiceWorkerGlobalScope.fonts Read only: Returns the FontFaceSet associated with the worker.
ServiceWorkerGlobalScope.indexedDB Read only: Provides a mechanism for applications to asynchronously access capabilities of indexed databases; returns an IDBFactory object.
ServiceWorkerGlobalScope.isSecureContext Read only: Returns a boolean indicating whether the current context is secure (true) or not (false).
ServiceWorkerGlobalScope.location Read only: Returns the WorkerLocation associated with the worker. WorkerLocation is a specific location object, mostly a subset of the Location for browsing scopes, but adapted to workers.
ServiceWorkerGlobalScope.navigator Read only: Returns the WorkerNavigator associated with the worker. WorkerNavigator is a specific navigator object, mostly a subset of the Navigator for browsing scopes, but adapted to workers.
ServiceWorkerGlobalScope.origin Read only: Returns the global object's origin, serialized as a string.
ServiceWorkerGlobalScope.performance Read only: Returns the Performance object associated with the worker, which is a regular performance object, but with a subset of its properties and methods available.
ServiceWorkerGlobalScope.scheduler Read only: Returns the Scheduler object associated with the current context. This is the entry point for using the Prioritized Task Scheduling API.
ServiceWorkerGlobalScope.self: Returns an object reference to the ServiceWorkerGlobalScope object itself.

Instance methods

This interface inherits methods from the WorkerGlobalScope interface, and its parent EventTarget.

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

Inherited from WorkerGlobalScope

ServiceWorkerGlobalScope.atob(): Decodes a string of data which has been encoded using base-64 encoding.
ServiceWorkerGlobalScope.btoa(): Creates a base-64 encoded ASCII string from a string of binary data.
ServiceWorkerGlobalScope.clearInterval(): Cancels the repeated execution set using setInterval.
ServiceWorkerGlobalScope.clearTimeout(): Cancels the repeated execution set using setTimeout.
ServiceWorkerGlobalScope.dump() Deprecated Non-standard: Writes a message to the console.
ServiceWorkerGlobalScope.importScripts(): Imports one or more scripts into the worker's scope. You can specify as many as you'd like, separated by commas. For example: importScripts('foo.js', 'bar.js');
ServiceWorkerGlobalScope.setInterval(): Schedules the execution of a function every X milliseconds.
ServiceWorkerGlobalScope.setTimeout(): Sets a delay for executing a function.

Events

activate: Occurs when a ServiceWorkerRegistration acquires a new ServiceWorkerRegistration.active worker.
backgroundfetchabort Experimental: Fired when a background fetch operation has been canceled by the user or the app.
backgroundfetchclick Experimental: Fired when the user has clicked on the UI for a background fetch operation.
backgroundfetchfail Experimental: Fired when at least one of the requests in a background fetch operation has failed.
backgroundfetchsuccess Experimental: Fired when all of the requests in a background fetch operation have succeeded.
canmakepayment Experimental: Fired on a payment app's service worker to check whether it is ready to handle a payment. Specifically, it is fired when the merchant website calls new PaymentRequest().
contentdelete Experimental: Occurs when an item is removed from the Content Index.
fetch: Occurs when a fetch() is called.
install: Occurs when a ServiceWorkerRegistration acquires a new ServiceWorkerRegistration.installing worker.
message: 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.
notificationclick: Occurs when a user clicks on a displayed notification.
notificationclose: Occurs when a user closes a displayed notification.
paymentrequest Experimental: Fired on a payment app when a payment flow has been initiated on the merchant website via the PaymentRequest.show() method.
sync: Triggered when a call to SyncManager.register is made from a service worker client page. The attempt to sync is made either immediately if the network is available or as soon as the network becomes available.
periodicsync Experimental: Occurs at periodic intervals, which were specified when registering a PeriodicSyncManager.
push: Occurs when a server push notification is received.
pushsubscriptionchange: Occurs when a push subscription has been invalidated, or is about to be invalidated (e.g. when a push service sets an expiration time).

Examples

This code snippet is from the service worker prefetch sample (see prefetch example live.) The 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", (event) => {
  console.log("Handling fetch event for", event.request.url);

  event.respondWith(
    caches.match(event.request).then((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(
        (response) => {
          console.log("Response from network is:", response);

          return response;
        },
        (error) => {
          console.error("Fetching failed:", error);

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

Specifications

Specification
Service Workers # serviceworkerglobalscope-interface

Browser compatibility

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