Offline works

src/service-worker.ts

@@ -1,20 +1,43 @@
 /* eslint-disable no-var */
 import { build, files, version } from '$service-worker';
 
-const worker = (self as unknown) as ServiceWorkerGlobalScope;
+// Code mostly comes from: https://dev.to/100lvlmaster/create-a-pwa-with-sveltekit-svelte-a36
+// With some modifications done by someone in the comments
 
-const FILES = `cache${version}`;
+const worker = (self as unknown) as ServiceWorkerGlobalScope;
+const STATIC_CACHE_NAME = `cache${version}`
+const APP_CACHE_NAME = `cache${version}`;
+
+// Hardcoded bunch of routes to always preemptively cache
+const routes = ["/", "/about"];
+
+// Hardcoded list of other assets to always preemptively cache
+const custom_assets = [
+  "https://fonts.googleapis.com/css2?family=Montserrat:wght@200&family=Roboto+Flex:opsz,wght@8..144,300;8..144,400;8..144,500&family=Roboto+Slab&display=swap"
+];
+
+// Adds the domain to the file path, making it a full name
+const addDomain = (assets: string[]) =>
+  assets.map((f) => self.location.origin + f);
 
 // build is an array of all files generated by the bundler
 // files is an array of all files in the static dir
-const to_cache = build.concat(files);
+const ourAssets = addDomain([
+  ...files,
+  ...build,
+  ...routes
+]);
+
+const to_cache = [...ourAssets, ...custom_assets]
 const staticAssets = new Set(to_cache);
 
 worker.addEventListener("install", (event) => {
   event.waitUntil(
     caches
-      .open(FILES)
-      .then((cache) => cache.addAll(to_cache))
+      .open(STATIC_CACHE_NAME)
+      .then((cache) => {
+        return cache.addAll(to_cache)
+      })
       .then(() => {
         worker.skipWaiting();
       })
@@ -27,7 +50,7 @@ worker.addEventListener("activate", (event) => {
       .then(async (keys) => {
         // Delete old caches
         for (const key of keys) {
-          if (key !== FILES) await caches.delete(key);
+          if (key !== STATIC_CACHE_NAME && key !== APP_CACHE_NAME) await caches.delete(key);
         }
         console.log("old caches deleted")
         worker.clients.claim();
@@ -39,7 +62,7 @@ worker.addEventListener("activate", (event) => {
 // Fetch the asset from the network and store it in the cache
 // Falls back to the cache if the user is offline
 async function fetchAndCache(request: Request) {
-  const cache = await caches.open(`offline${version}`);
+  const cache = await caches.open(APP_CACHE_NAME);
 
   try {
     const response = await fetch(request);
@@ -57,7 +80,7 @@ async function fetchAndCache(request: Request) {
 worker.addEventListener("fetch", (event) => {
   if (event.request.method !== "GET") return;
 
-  console.log("fetch event intercepted")
+  //console.log("fetch event intercepted")
 
   // Firefox has not yet fixed this, so it needs to be excluded from this caching behavior
   // https://web.dev/sw-range-requests/
@@ -68,12 +91,15 @@ worker.addEventListener("fetch", (event) => {
 
   // Don't try to cache protocols other than http/https
   const isHttp = url.protocol.startsWith("http");
-  const isStaticAsset = url.host === self.location.host && staticAssets.has(url.pathname);
+  const isStaticAsset = staticAssets.has(url.href);
   const skipBecauseUncached = event.request.cache === 'only-if-cached' && !isStaticAsset;
 
   if (isHttp && !skipBecauseUncached) {
     event.respondWith(
       (async () => {
+        // always serve static files and bundler-generated assets from cache.
+        // if your application has other URLs with data that will never change,
+        // set this variable to true for them, and they will only be fetched once.
         const cachedAsset = isStaticAsset && (await caches.match(event.request));
 
         return cachedAsset || fetchAndCache(event.request);