web api overview
Web Periodic Background Synchronization API
Secure contextLimited availabilityAvailable in workers
The Web Periodic Background Synchronization API provides a way to register tasks to be run in a service worker at periodic intervals with network connectivity. These tasks are referred to as periodic background sync requests.
Concepts and Usage
The Periodic Background Sync API allows web applications to alert their service worker to make any updates, at a periodic time interval. Uses may include fetching latest content while a device is connected to Wi-Fi, or allowing background updates to an application.
The minimum time interval is set when the API is invoked; however the user agent might also take into account other factors which affect when the service worker receives the event. For instance previous website engagement, or connection to a known network.
The PeriodicSyncManager interface is available through periodicSync. A unique tag identifier is set to ‘name’ the sync event, which can then be listened for within the ServiceWorker script. Once the event is received you can then run any functionality available, such as updating caches or fetching new resources.
As this API relies on service workers, functionality provided by this API is only available in a secure context.
Interfaces
PeriodicSyncManagerExperimental- : Registers tasks to be run in a service worker at periodic intervals with network connectivity. These tasks are referred to as periodic background sync requests.
PeriodicSyncEventExperimental- : Represents a synchronization event, sent to the
global scopeof aServiceWorker. It provides a way to run tasks in the service worker with network connectivity.
- : Represents a synchronization event, sent to the
Extensions to other interfaces
The following additions to the Service Worker API are specified in the Periodic Background Sync specification to provide an entry point for using Periodic Background Sync.
periodicSyncRead only Experimental- : Returns a reference to the
PeriodicSyncManagerinterface for registering tasks to run at specific intervals.
- : Returns a reference to the
periodicsyncevent Experimental- : Occurs at periodic intervals, which were specified when registering a
PeriodicSyncManager.
- : Occurs at periodic intervals, which were specified when registering a
Examples
The following examples show how to use the interface.
Requesting a Periodic Background Sync
The following asynchronous function registers a periodic background sync at a minimum interval of one day from a browsing context:
async function registerPeriodicNewsCheck() {
const registration = await navigator.serviceWorker.ready;
try {
await registration.periodicSync.register("get-latest-news", {
minInterval: 24 * 60 * 60 * 1000,
});
} catch {
console.log("Periodic Sync could not be registered!");
}
}
Verifying a Background Periodic Sync by Tag
This code checks to see if a Periodic Background Sync task with a given tag is registered.
navigator.serviceWorker.ready.then((registration) => {
registration.periodicSync.getTags().then((tags) => {
if (tags.includes("get-latest-news")) skipDownloadingLatestNewsOnPageLoad();
});
});
Removing a Periodic Background Sync Task
The following code removes a Periodic Background Sync task to stop articles syncing in the background.
navigator.serviceWorker.ready.then((registration) => {
registration.periodicSync.unregister("get-latest-news");
});
Listening for a Periodic Background Sync within a Service Worker
The following example shows how to respond to a periodic sync event in the service worker.
self.addEventListener("periodicsync", (event) => {
if (event.tag === "get-latest-news") {
event.waitUntil(fetchAndCacheLatestNews());
}
});