sw.js

const VERSION = 'v1';

self.addEventListener('install', event => {
    event.waitUntil(precache());
});

self.addEventListener('fetch', event => {
    const request = event.request;
    if (request.method !== 'GET') {
        return;
    }
    event.respondWith(cachedResponse(request));
    event.waitUntil(updateCache(request));
})

async function precache () {
    const cache = await caches.open(VERSION);
    return cache.addAll(
        [/*
            '/',
            './index.html',
            './assets/BigBuckBunny.mp4',
            './assets/style.css',         
            './assets/script.js',
            './assets/mediaPlayer.js',
            './assets/plugins/autoPause.js',
            './assets/plugins/autoPlay.js'
        */]
    );
}

async function cachedResponse (request) {
    const cache = await caches.open(VERSION);
    const response = await cache.match(request);
    return response || fetch(request);
}

async function updateCache(request) {
    const cache = await caches.open(VERSION);
    const response = await fetch(request);
    return cache.put(request, response);
}