Flight lookup: OpenSky live data, i18n, PWA, visual redesign

sw.js

@@ -0,0 +1,49 @@
+const CACHE_NAME = "flight-lookup-v1";
+const ASSETS = [
+  "./",
+  "./index.html",
+  "./style.css",
+  "./data.js",
+  "./app.js",
+  "./manifest.json"
+];
+
+self.addEventListener("install", (event) => {
+  event.waitUntil(
+    caches.open(CACHE_NAME).then((cache) => cache.addAll(ASSETS))
+  );
+  self.skipWaiting();
+});
+
+self.addEventListener("activate", (event) => {
+  event.waitUntil(
+    caches.keys().then((keys) =>
+      Promise.all(
+        keys
+          .filter((k) => k !== CACHE_NAME)
+          .map((k) => caches.delete(k))
+      )
+    )
+  );
+  self.clients.claim();
+});
+
+self.addEventListener("fetch", (event) => {
+  const { request } = event;
+  if (request.method !== "GET") return;
+
+  event.respondWith(
+    caches.match(request).then((cached) => {
+      if (cached) return cached;
+      return fetch(request)
+        .then((response) => {
+          if (response.ok && request.url.startsWith(self.location.origin)) {
+            const clone = response.clone();
+            caches.open(CACHE_NAME).then((cache) => cache.put(request, clone));
+          }
+          return response;
+        })
+        .catch(() => caches.match("./index.html"));
+    })
+  );
+});