blob: f5ed1899d495a1befe78296b0cea9c1ea36f26ea [file] [log] [blame]
avm999631b637612018-12-28 01:03:44 +01001/*
2 Copyright 2015 Google Inc. All Rights Reserved.
3 Licensed under the Apache License, Version 2.0 (the "License");
4 you may not use this file except in compliance with the License.
5 You may obtain a copy of the License at
6 http://www.apache.org/licenses/LICENSE-2.0
7 Unless required by applicable law or agreed to in writing, software
8 distributed under the License is distributed on an "AS IS" BASIS,
9 WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
10 See the License for the specific language governing permissions and
11 limitations under the License.
12*/
13
14'use strict';
15
16// Incrementing CACHE_VERSION will kick off the install event and force previously cached
17// resources to be cached again.
18const CACHE_VERSION = 1;
19let CURRENT_CACHES = {
20 offline: 'offline-v' + CACHE_VERSION
21};
22const OFFLINE_URL = 'offline.html';
23
24function createCacheBustedRequest(url) {
25 let request = new Request(url, {cache: 'reload'});
26 // See https://fetch.spec.whatwg.org/#concept-request-mode
27 // This is not yet supported in Chrome as of M48, so we need to explicitly check to see
28 // if the cache: 'reload' option had any effect.
29 if ('cache' in request) {
30 return request;
31 }
32
33 // If {cache: 'reload'} didn't have any effect, append a cache-busting URL parameter instead.
34 let bustedUrl = new URL(url, self.location.href);
35 bustedUrl.search += (bustedUrl.search ? '&' : '') + 'cachebust=' + Date.now();
36 return new Request(bustedUrl);
37}
38
39self.addEventListener('install', event => {
40 event.waitUntil(
41 // We can't use cache.add() here, since we want OFFLINE_URL to be the cache key, but
42 // the actual URL we end up requesting might include a cache-busting parameter.
43 fetch(createCacheBustedRequest(OFFLINE_URL)).then(function(response) {
44 return caches.open(CURRENT_CACHES.offline).then(function(cache) {
45 return cache.put(OFFLINE_URL, response);
46 });
47 })
48 );
49});
50
51self.addEventListener('activate', event => {
52 // Delete all caches that aren't named in CURRENT_CACHES.
53 // While there is only one cache in this example, the same logic will handle the case where
54 // there are multiple versioned caches.
55 let expectedCacheNames = Object.keys(CURRENT_CACHES).map(function(key) {
56 return CURRENT_CACHES[key];
57 });
58
59 event.waitUntil(
60 caches.keys().then(cacheNames => {
61 return Promise.all(
62 cacheNames.map(cacheName => {
63 if (expectedCacheNames.indexOf(cacheName) === -1) {
64 // If this cache name isn't present in the array of "expected" cache names,
65 // then delete it.
66 console.log('Deleting out of date cache:', cacheName);
67 return caches.delete(cacheName);
68 }
69 })
70 );
71 })
72 );
73});
74
75self.addEventListener('fetch', event => {
76 // We only want to call event.respondWith() if this is a navigation request
77 // for an HTML page.
78 // request.mode of 'navigate' is unfortunately not supported in Chrome
79 // versions older than 49, so we need to include a less precise fallback,
80 // which checks for a GET request with an Accept: text/html header.
81 if (event.request.mode === 'navigate' ||
82 (event.request.method === 'GET' &&
83 event.request.headers.get('accept').includes('text/html'))) {
84 console.log('Handling fetch event for', event.request.url);
85 event.respondWith(
86 fetch(event.request).catch(error => {
87 // The catch is only triggered if fetch() throws an exception, which will most likely
88 // happen due to the server being unreachable.
89 // If fetch() returns a valid HTTP response with an response code in the 4xx or 5xx
90 // range, the catch() will NOT be called. If you need custom handling for 4xx or 5xx
91 // errors, see https://github.com/GoogleChrome/samples/tree/gh-pages/service-worker/fallback-response
92 console.log('Fetch failed; returning offline page instead.', error);
93 return caches.match(OFFLINE_URL);
94 })
95 );
96 }
97
98 // If our if() condition is false, then this fetch handler won't intercept the request.
99 // If there are any other fetch handlers registered, they will get a chance to call
100 // event.respondWith(). If no fetch handlers call event.respondWith(), the request will be
101 // handled by the browser as if there were no service worker involvement.
102});