try to make install work by caching

src/main/resources/web/js/notification.js

@@ -40,4 +40,4 @@ function authNotification(msg, yes, no) {
         };
         setTimeout(() => { delete notificationCallbacks[tag] }, 30 * 1000);
     });
-}
+}

src/main/resources/web/js/page.js

@@ -13,7 +13,13 @@ window.addEventListener('beforeinstallprompt', e => {
 // On load
 $(() => {
     if (navigator.serviceWorker) {
-        navigator.serviceWorker.register("sw.js");
+        navigator.serviceWorker.register("sw.js")
+            .then(it => it.installing.postMessage({
+                action: "cache",
+                urls: performance.getEntriesByType("resource")
+                    .map(it => it.name)
+                    .filter(it => it.endsWith(".js") || it.endsWith(".css") || it.endsWith(".png"))
+            })); // https://stackoverflow.com/questions/46830493/is-there-any-way-to-cache-all-files-of-defined-folder-path-in-service-worker
     }
 
     ohNo();

src/main/resources/web/sw.js

@@ -6,6 +6,37 @@ self.addEventListener("notificationclick", event => {
   viac.postMessage({tag: event.notification.tag, action: event.action});
 });
 
-addEventListener("fetch", e => {
-  // chrome please show "add to home screen"
+// stolen from https://github.com/mozilla/serviceworker-cookbook/blob/master/strategy-network-or-cache/service-worker.js (MIT license)
+
+var CACHE = "network-or-cache";
+
+self.addEventListener("install", evt => {
+  evt.waitUntil(cache(["./"]));
 });
+
+self.addEventListener("fetch", evt => {
+  evt.respondWith(
+    fromNetwork(evt.request)
+      .catch(() => fromCache(evt.request))
+  );
+});
+
+addEventListener("message", e => {
+  if (e.data.action == "cache") {
+    event.waitUntil(cache(e.data.urls));
+  }
+});
+
+function cache(urls) {
+  return caches.open(CACHE).then(cache => cache.addAll(urls));
+}
+
+function fromNetwork(request) {
+  return fetch(request);
+}
+
+function fromCache(request) {
+  return caches.open(CACHE)
+    .then(cache => cache.match(request))
+    .then(matching => matching || Promise.reject("no-match"));
+}