BackgroundFetchUpdateUIEvent

Limited availability

This feature is not Baseline because it does not work in some of the most widely-used browsers.

Experimental: This is an experimental technology
Check the Browser compatibility table carefully before using this in production.

Note: This feature is only available in Service Workers.

The BackgroundFetchUpdateUIEvent interface of the Background Fetch API is an event type for the backgroundfetchsuccess and backgroundfetchfail events, and provides a method for updating the title and icon of the app to inform a user of the success or failure of a background fetch.

Event ExtendableEvent BackgroundFetchEvent BackgroundFetchUpdateUIEvent

Constructor

BackgroundFetchUpdateUIEvent()

Creates a new BackgroundFetchUIEvent object. This constructor is not typically used, as the browser creates these objects itself for the backgroundfetchsuccess and backgroundfetchfail events.

Instance properties

Also inherits properties from its parent, BackgroundFetchEvent.

Instance methods

Also inherits methods from its parent, BackgroundFetchEvent.

BackgroundFetchUpdateUIEvent.updateUI()

Updates the title and icon in the user interface to show the status of a background fetch. Resolves with a Promise.

Examples

In this example, the backgroundfetchsuccess event is listened for, indicating that a fetch has completed successfully. The updateUI() method is then called, with a message to let the user know the episode they downloaded is ready.

js
addEventListener("backgroundfetchsuccess", (event) => {
  const bgFetch = event.registration;

  event.waitUntil(
    (async () => {
      // Create/open a cache.
      const cache = await caches.open("downloads");
      // Get all the records.
      const records = await bgFetch.matchAll();
      // Copy each request/response across.
      const promises = records.map(async (record) => {
        const response = await record.responseReady;
        await cache.put(record.request, response);
      });

      // Wait for the copying to complete.
      await Promise.all(promises);

      // Update the progress notification.
      event.updateUI({ title: "Episode 5 ready to listen!" });
    })(),
  );
});