Add PWA + ServiceWorker with offline support

public/sw.js

@@ -0,0 +1,45 @@
+const OFFLINE_VERSION = 1;
+const CACHE_NAME = "offline";
+const OFFLINE_URL = "/offline.html";
+
+self.addEventListener("install", (event) => {
+	event.waitUntil(
+		(async () => {
+			const cache = await caches.open(CACHE_NAME);
+			await cache.add(new Request(OFFLINE_URL, { cache: "reload" }));
+		})()
+	);
+	self.skipWaiting();
+});
+
+self.addEventListener("activate", (event) => {
+	event.waitUntil(
+		(async () => {
+			if ("navigationPreload" in self.registration) {
+				await self.registration.navigationPreload.enable();
+			}
+		})()
+	);
+	self.clients.claim();
+});
+
+self.addEventListener("fetch", (event) => {
+	if (event.request.mode === "navigate") {
+		event.respondWith(
+			(async () => {
+				try {
+					const preloadResponse = await event.preloadResponse;
+					if (preloadResponse) {
+						return preloadResponse;
+					}
+					const networkResponse = await fetch(event.request);
+					return networkResponse;
+				} catch (error) {
+					const cache = await caches.open(CACHE_NAME);
+					const cachedResponse = await cache.match(OFFLINE_URL);
+					return cachedResponse;
+				}
+			})()
+		);
+	}
+});

resources/assets/js/app.js

@@ -34,6 +34,12 @@ window.App.boot = function() {
 	new Vue({ el: '#content'});
 }
 
+window.addEventListener("load", () => {
+  if ("serviceWorker" in navigator) {
+    navigator.serviceWorker.register("/sw.js");
+  }
+});
+
 window.App.util = {
 	compose: {
 		post: (function() {