Service Worker to make the site offline

worker.js

var version = 'v1::';

// -------------------------------------------------------
// aqui devem ser baixados os recursos offline, que devem vir de uma lista em algum local
// provavelmente alguma API no site
this.addEventListener('install', function(event) {
    console.log('Service Worker instalado!');

    // return self.clients.skipWaiting();
});

this.addEventListener('activate', function(event) {
    console.log('Service worker ativado!');

    return self.clients.claim();
});

this.addEventListener('fetch', function(event) {
    event.respondWith(
        caches.match(event.request).then(function(response) {
            return response || fetch(event.request);
        }).catch(function(error) {
            console.log(event.request.url, error);
        })
    );
});

this.addEventListener('message', function(event) {
    // -------------------------------------------------------
    // this is a function called when the 'refresh offline site' its called
    if (event.data.action === 'update') {
        caches.keys().then(function(keys) {
            return Promise.all(keys.map(function(key) {
                return caches.delete(keys[key]);
            }));
        });
        
        // this endpoint returns all URLs and imagens that must me cached
        fetch('/ajax/offline', {mode: 'no-cors', cache: 'no-cache'}).then(function(response) {
            return response.json();
        }).then(function(resources) {
            return caches.open(version).then(function(cache) {
                return cache.addAll(resources);
            });
        }).then(function() {
            event.ports[0].postMessage({completed: true});
            console.log('cache atualzado!');
        });
    }

    // -------------------------------------------------------
    // clearing the cache
    if (event.data.action === 'clear') {
        caches.keys().then(function(keys) {
            return Promise.all(keys.map(function(key) {
                return caches.delete(keys[key]);
            }));
        }).then(function() {
            event.ports[0].postMessage({completed: true});
            console.log('cache limpo!');
        });
    }
});