browser.js/packages/sandbox/controller.html

<title>Proxy Sandbox Controller</title>
<script>
	function wake(controller) {
		window.parent.postMessage({ $sandboxsw$type: "ready" }, "*");
	}
	navigator.serviceWorker
		.register("/sw.js", {
			scope: "./",
		})
		.then((registration) => {
			if (navigator.serviceWorker.controller) {
				// there's probably already a service worker
				wake(navigator.serviceWorker.controller);
			} else {
				// there's no service worker, wait until we're controlled
				navigator.serviceWorker.addEventListener("controllerchange", () => {
					wake(navigator.serviceWorker.controller);
				});
			}
		})
		.catch((error) => {
			console.error("Service Worker registration failed:", error);
			window.parent.postMessage(
				{ $sandboxsw$type: "initerror", message: error.message },
				"*"
			);
		});

	// chrome -> controller -> service worker
	window.addEventListener("message", (event) => {
		if (!navigator.serviceWorker.controller) {
			console.error("No service worker controller to send message to.");
			return;
		}

		// forward messageport
		navigator.serviceWorker.controller.postMessage(event.data, event.ports);
	});
</script>