1// In production, we register a service worker to serve assets from local cache.
2
3// This lets the app load faster on subsequent visits in production, and gives
4// it offline capabilities. However, it also means that developers (and users)
5// will only see deployed updates on the "N+1" visit to a page, since previously
6// cached resources are updated in the background.
7
8// To learn more about the benefits of this model, read https://goo.gl/KwvDNy.
9// This link also includes instructions on opting out of this behavior.
10
11const isLocalhost = Boolean(
12 window.location.hostname === 'localhost' ||
13 // [::1] is the IPv6 localhost address.
14 window.location.hostname === '[::1]' ||
15 // 127.0.0.1/8 is considered localhost for IPv4.
16 window.location.hostname.match(
17 /^127(?:\.(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)){3}$/
18 )
19);
20
21export default function register() {
22 if (process.env.NODE_ENV === 'production' && 'serviceWorker' in navigator) {
23 // The URL constructor is available in all browsers that support SW.
24 const publicUrl = new URL(process.env.PUBLIC_URL, window.location);
25 if (publicUrl.origin !== window.location.origin) {
26 // Our service worker won't work if PUBLIC_URL is on a different origin
27 // from what our page is served on. This might happen if a CDN is used to
28 // serve assets; see https://github.com/facebookincubator/create-react-app/issues/2374
29 return;
30 }
31
32 window.addEventListener('load', () => {
33 const swUrl = `${process.env.PUBLIC_URL}/service-worker.js`;
34
35 if (isLocalhost) {
36 // This is running on localhost. Lets check if a service worker still exists or not.
37 checkValidServiceWorker(swUrl);
38
39 // Add some additional logging to localhost, pointing developers to the
40 // service worker/PWA documentation.
41 navigator.serviceWorker.ready.then(() => {
42 console.log(
43 'This web app is being served cache-first by a service ' +
44 'worker. To learn more, visit https://goo.gl/SC7cgQ'
45 );
46 });
47 } else {
48 // Is not local host. Just register service worker
49 registerValidSW(swUrl);
50 }
51 });
52 }
53}
54
55function registerValidSW(swUrl) {
56 navigator.serviceWorker
57 .register(swUrl)
58 .then(registration => {
59 registration.onupdatefound = () => {
60 const installingWorker = registration.installing;
61 installingWorker.onstatechange = () => {
62 if (installingWorker.state === 'installed') {
63 if (navigator.serviceWorker.controller) {
64 // At this point, the old content will have been purged and
65 // the fresh content will have been added to the cache.
66 // It's the perfect time to display a "New content is
67 // available; please refresh." message in your web app.
68 console.log('New content is available; please refresh.');
69 } else {
70 // At this point, everything has been precached.
71 // It's the perfect time to display a
72 // "Content is cached for offline use." message.
73 console.log('Content is cached for offline use.');
74 }
75 }
76 };
77 };
78 })
79 .catch(error => {
80 console.error('Error during service worker registration:', error);
81 });
82}
83
84function checkValidServiceWorker(swUrl) {
85 // Check if the service worker can be found. If it can't reload the page.
86 fetch(swUrl)
87 .then(response => {
88 // Ensure service worker exists, and that we really are getting a JS file.
89 if (
90 response.status === 404 ||
91 response.headers.get('content-type').indexOf('javascript') === -1
92 ) {
93 // No service worker found. Probably a different app. Reload the page.
94 navigator.serviceWorker.ready.then(registration => {
95 registration.unregister().then(() => {
96 window.location.reload();
97 });
98 });
99 } else {
100 // Service worker found. Proceed as normal.
101 registerValidSW(swUrl);
102 }
103 })
104 .catch(() => {
105 console.log(
106 'No internet connection found. App is running in offline mode.'
107 );
108 });
109}
110
111export function unregister() {
112 if ('serviceWorker' in navigator) {
113 navigator.serviceWorker.ready.then(registration => {
114 registration.unregister();
115 });
116 }
117}