Service Workers Cached JS

offline.svg

sw.js

'use strict';
const version = 'v201704100047';
const __DEVELOPMENT__ = false;
const __DEBUG__ = false;
const offlineResources = ['/', '/offline.html', '/offline.svg'];
const ignoreFetch = [/https?:\/\/example.disqus.com\//, /chrome-extension:\/\//];

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);