sw.js

"use strict";
const cacheNamespace = "planning-poker";
const version = "v1.0.0";
const cacheName = `${cacheNamespace}-${version}-static`;

function updateStaticCache() {
    return caches.open(cacheName).then(cache => {
        return cache.addAll([
            "./style.css",
            "./",
            "./manifest.json",
            "images/planning-poker.png",
            "images/planning-poker.svg"
        ]);
    });
}

function clearOldCaches() {
    return caches.keys().then(keys => {
        return Promise.all(
            keys
                .filter(key => key.indexOf(cacheNamespace) === 0)
                .filter(key => key.indexOf(cacheName) !== 0)
                .map(key => caches.delete(key))
        );
    });
}

self.addEventListener("install", event => {
    event.waitUntil(updateStaticCache().then(() => self.skipWaiting()));
});

self.addEventListener("activate", event => {
    event.waitUntil(clearOldCaches().then(() => self.clients.claim()));
});

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

    if (url.origin !== location.origin) {
        return;
    }

    // try cache firts, fall back to network
    event.respondWith(
        caches.match(request).then(response => {
            return (
                response ||
                fetch(request)
                    .then(response => {
                        const copy = response.clone();
                        stashInCache(cacheName, request, copy);
                        return response;
                    })
                    .catch(() => {
                        return;
                    })
            );
        })
    );
});