sw.js

'use strict';
const version = 'v20170505';
const __DEVELOPMENT__ = false;
const __DEBUG__ = false;
const offlineResources = [
  '/',
  '/offline.html',
  '/offline.svg',
];

const ignoreFetch = [
    /https?:\/\/busuanzi.ibruce.info\//,
    /https?:\/\/dn-lbstatics.qbox.me\//,
    /https?:\/\/fonts.gstatic.com\//,
];

function onInstall(event) {
    log('install event in progress.');
    event.waitUntil(updateStaticCache());
    self.skipWaiting()
}

function updateStaticCache() {
    return caches.open(cacheKey('offline')).then((cache) => {
        return cache.addAll(offlineResources)
    }).then(() => {
        log('installation complete!')
    })
}

function onFetch(event) {
    const request = event.request;
    if (shouldAlwaysFetch(request)) {
        event.respondWith(networkedOrOffline(request));
        return
    }
    if (shouldFetchAndCache(request)) {
        event.respondWith(networkedOrCached(request));
        return
    }
    event.respondWith(cachedOrNetworked(request))
}

function networkedOrCached(request) {
    return networkedAndCache(request).catch(() => {
        return cachedOrOffline(request)
    })
}

function networkedAndCache(request) {
    return fetch(request).then((response) => {
        var copy = response.clone();
        caches.open(cacheKey('resources')).then((cache) => {
            cache.put(request, copy)
        });
        log("(network: cache write)", request.method, request.url);
        return response
    })
}

function cachedOrNetworked(request) {
    return caches.match(request).then((response) => {
        log(response ? '(cached)' : '(network: cache miss)', request.method, request.url);
        return response || networkedAndCache(request).catch(() => {
            return offlineResponse(request)
        })
    })
}

function networkedOrOffline(request) {
    return fetch(request).then((response) => {
        log('(network)', request.method, request.url);
        return response
    }).catch(() => {
        return offlineResponse(request)
    })
}

function cachedOrOffline(request) {
    return caches.match(request).then((response) => {
        return response || offlineResponse(request)
    })
}

function offlineResponse(request) {
    log('(offline)', request.method, request.url);
    if (request.url.match(/\.(jpg|png|gif|svg|jpeg)(\?.*)?$/)) {
        return caches.match('/offline.svg')
    } else {
        return caches.match('/offline.html')
    }
}

function onActivate(event) {
    log('activate event in progress.');
    event.waitUntil(removeOldCache())
}

function removeOldCache() {
    return caches.keys().then((keys) => {
        return Promise.all(keys.filter((key) => {
            return !key.startsWith(version)
        }).map((key) => {
            return caches.delete(key)
        }))
    }).then(() => {
        log('removeOldCache completed.')
    })
}

function cacheKey() {
    return [version, ...arguments].join(':')
}

function log() {
    if (developmentMode()) {
        console.log("SW:", ...arguments)
    }
}

function shouldAlwaysFetch(request) {
    return __DEVELOPMENT__ || request.method !== 'GET' || ignoreFetch.some(regex => request.url.match(regex))
}

function shouldFetchAndCache(request) {
    return ~request.headers.get('Accept').indexOf('text/html')
}

function developmentMode() {
    return __DEVELOPMENT__ || __DEBUG__
}
log("Hello from ServiceWorker land!", version);
self.addEventListener('install', onInstall);
self.addEventListener('fetch', onFetch);
self.addEventListener("activate", onActivate);