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 onfetch
or 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
.
Properties
ServiceWorkerGlobalScope.caches
Read only-
Contains the
CacheStorage
object associated with the service worker. 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.
Events
activate
-
Occurs when a
ServiceWorkerRegistration
acquires a newServiceWorkerRegistration.active
worker. contentdelete
-
Occurs when an item is removed from the
Content Index
. fetch
-
Occurs when a
fetch()
is called. install
-
Occurs when a
ServiceWorkerRegistration
acquires a newServiceWorkerRegistration.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 theMessagePort
exposed inevent.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.
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
-
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).
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
. Therefore it also has the following property available to it:
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', 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;
}, function(error) {
console.error('Fetching failed:', error);
throw error;
});
})
);
});
Specifications
Specification |
---|
Service Workers 1 # serviceworkerglobalscope-interface |
Browser compatibility
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