periodic sync example code

1.js

// ..

self.addEventListener("periodicsync",onPeriodicSync);

// ..

await registerPeriodicSync();

// ..

async function registerPeriodicSync() {
	try {
		// periodic sync supported?
		if ("periodicSync" in self.registration) {
			let status = await navigator.permissions.query({
				name: "periodic-background-sync",
			});

			// periodic sync allowed?
			if (status.state == "granted") {
				let tags = await self.registration.periodicSync.getTags();

				// daily sync hasn't been registered yet?
				if (!tags.includes("daily-sync")) {
					await self.registration.periodicSync.register("daily-sync",{
						// periodic update-check once per day
						minInterval: 24 * 60 * 60 * 1000,
					});

					console.log("sync event registered!");
				}
			}
		}
	}
	catch (err) {}
}

function onPeriodicSync(event) {
	if (event.tag == "daily-sync") {
		console.log(`periodic-sync-event: ${event.tag}`);

		event.waitUntil(Promise.all([
			// check the service-worker on the server to see
			// if it's been updated
			self.registration.update(),
			(
				// show the app-icon badge (daily reminder)?
				navigator.setAppBadge ?
					navigator.setAppBadge() :
					undefined
			),
			// temporary periodic-sync event logging (on the server)
			router(new Request("/pse")),
		]));
	}
}

// ..

Thanks for sharing! Kyle
For future readers; this https://developer.mozilla.org/en-US/docs/Web/API/Web_Periodic_Background_Synchronization_API (MDN article) should be a great place to explore more.