PWA.

public/index.html

@@ -33,7 +33,7 @@
         if ("serviceWorker" in navigator) {
             window.addEventListener("load", function () {
                 navigator.serviceWorker
-                    .register("worker.js")
+                    .register("js/worker.js")
                     .then(
                         function (registration) {
                             console.log("Worker registration successful", registration.scope);

public/js/worker.js

@@ -0,0 +1,51 @@
+// Flag for enabling cache in production
+var doCache = false;
+
+var CACHE_NAME = "pwa-app-cache";
+
+// Delete old caches
+self.addEventListener("activate", (event) => {
+    const currentCachelist = [CACHE_NAME];
+    event.waitUntil(
+        caches.keys().then((keyList) =>
+            Promise.all(
+                keyList.map((key) => {
+                    if (!currentCachelist.includes(key)) {
+                        return caches.delete(key);
+                    }
+                })
+            )
+        )
+    );
+});
+
+// This triggers when user starts the app
+self.addEventListener("install", function (event) {
+    if (doCache) {
+        event.waitUntil(
+            caches.open(CACHE_NAME).then(function (cache) {
+                fetch("asset-manifest.json")
+                    .then((response) => {
+                        response.json();
+                    })
+                    .then((assets) => {
+                        // We will cache initial page and the main.js
+                        // We could also cache assets like CSS and images
+                        const urlsToCache = ["/", assets["main.js"]];
+                        cache.addAll(urlsToCache);
+                    });
+            })
+        );
+    }
+});
+
+// Here we intercept request and serve up the matching files
+self.addEventListener("fetch", function (event) {
+    if (doCache) {
+        event.respondWith(
+            caches.match(event.request).then(function (response) {
+                return response || fetch(event.request);
+            })
+        );
+    }
+});