service-worker.js

importScripts('js/cache-polyfill.js');

var CACHE_VERSION = 'app-v1';
var CACHE_FILES = [
    'index.html',
    'ppt.html',
    'service-worker.js',
    'js/app.js',
    'js/impress.js',
    'js/cache-polyfill.js',
    'images/background.jpeg',
    'images/serviceWorker.png',
    'css/ppt.css',
    'css/reset.css',
    'css/styles.css',
    'css/Roboto.woff2',
];


self.addEventListener('install', function (event) {
    console.log('install', event)
    event.waitUntil(
        caches.open(CACHE_VERSION)
            .then(function (cache) {
                console.log('Opened cache');
                return cache.addAll(CACHE_FILES);
            })
    );
});

self.addEventListener('activate', function (event) {
    console.log('activate', event)
    event.waitUntil(
        caches.keys().then(function (keys) {
            return Promise.all(keys.map(function (key, i) {
                if (key !== CACHE_VERSION) {
                    return caches.delete(keys[i]);
                }
            }))
        })
    )
});

self.addEventListener('fetch', function (event) {
    console.log('fetch', event)
    event.respondWith(
        caches.match(event.request).then(function (res) {
            if (res) return res;
            requestBackend(event);
        })
    )
});

function requestBackend (event) {
    console.log('requestBackend', event)
    var url = event.request.clone();
    return fetch(url).then(function (res) {
        //if not a valid response send the error
        if (!res || res.status !== 200 || res.type !== 'basic') return res;

        var response = res.clone();

        caches.open(CACHE_VERSION).then(function (cache) {
            cache.put(event.request, response);
        });

        return res;
    })
}