NHL-Scoreboard/app/static/sw.js

const CACHE = 'nhl-scoreboard-v1';
const PRECACHE = [
    '/',
    '/static/styles.css',
    '/static/script.js',
    '/static/icon-192x192.png',
    '/static/icon-512x512.png',
    '/manifest.json',
];

self.addEventListener('install', event => {
    event.waitUntil(caches.open(CACHE).then(c => c.addAll(PRECACHE)));
    self.skipWaiting();
});

self.addEventListener('activate', event => {
    event.waitUntil(
        caches.keys().then(keys =>
            Promise.all(keys.filter(k => k !== CACHE).map(k => caches.delete(k)))
        )
    );
    self.clients.claim();
});

self.addEventListener('fetch', event => {
    const { pathname } = new URL(event.request.url);

    // Network-first for the live scoreboard API — stale data is useless
    if (pathname === '/scoreboard') {
        event.respondWith(
            fetch(event.request).catch(() => caches.match(event.request))
        );
        return;
    }

    // Cache-first for everything else (static assets, shell)
    event.respondWith(
        caches.match(event.request).then(cached => {
            if (cached) return cached;
            return fetch(event.request).then(response => {
                if (response.ok) {
                    const clone = response.clone();
                    caches.open(CACHE).then(c => c.put(event.request, clone));
                }
                return response;
            });
        })
    );
});