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.
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.
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.
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.
Returns the Performance object associated with the worker, which is a regular performance object, but with a subset of its properties and methods available.
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');
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().
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.
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.
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…");returnfetch(event.request).then((response)=>{
console.log("Response from network is:", response);return response;},(error)=>{
console.error("Fetching failed:", error);throw error;});}));});