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ServiceWorkerGlobalScope: sync event

files/en-us/web/api/serviceworkerglobalscope/sync_event/index.md

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{{APIRef("Background Sync")}}{{SecureContext_Header}}{{AvailableInWorkers("service")}}

The sync event of the {{domxref("ServiceWorkerGlobalScope")}} interface is fired when the page (or worker) that registered the event with the {{domxref('SyncManager')}} is running and as soon as network connectivity is available.

This event is not cancelable and does not bubble.

Syntax

Use the event name in methods like {{domxref("EventTarget.addEventListener", "addEventListener()")}}, or set an event handler property.

js-nolint
addEventListener("sync", (event) => { })

onsync = (event) => { }

Event type

A {{domxref("SyncEvent")}}. Inherits from {{domxref("ExtendableEvent")}} and {{domxref("Event")}}.

{{InheritanceDiagram("SyncEvent")}}

Event properties

Inherits properties from its ancestor, {{domxref("ExtendableEvent")}} and {{domxref("Event")}}.

  • {{domxref("SyncEvent.tag")}} {{ReadOnlyInline}}
    • : Returns the developer-defined identifier for this SyncEvent.
  • {{domxref("SyncEvent.lastChance")}} {{ReadOnlyInline}}
    • : Returns true if the user agent will not make further synchronization attempts after the current attempt.

Examples

The following example shows how to respond to a sync event in the service worker.

js
self.addEventListener("sync", (event) => {
  if (event.tag === "sync-messages") {
    event.waitUntil(sendOutboxMessages());
  }
});

You can also set up the event handler using the onsync property:

js
self.onsync = (event) => {
  // …
};

Specifications

{{Specifications}}

Browser compatibility

{{Compat}}

See also