1// This optional code is used to register a service worker.
2// register() is not called by default.
3
4// This lets the app load faster on subsequent visits in production, and gives
5// it offline capabilities. However, it also means that developers (and users)
6// will only see deployed updates on subsequent visits to a page, after all the
7// existing tabs open on the page have been closed, since previously cached
8// resources are updated in the background.
9
10// To learn more about the benefits of this model and instructions on how to
11// opt-in, read https://bit.ly/CRA-PWA
12
13const isLocalhost = Boolean(
14 window.location.hostname === 'localhost' ||
15 // [::1] is the IPv6 localhost address.
16 window.location.hostname === '[::1]' ||
17 // 127.0.0.0/8 are considered localhost for IPv4.
18 window.location.hostname.match(/^127(?:\.(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)){3}$/)
19);
20
21type Config = {
22 onSuccess?: (registration: ServiceWorkerRegistration) => void;
23 onUpdate?: (registration: ServiceWorkerRegistration) => void;
24};
25
26export function register(config?: Config) {
27 if (process.env.NODE_ENV === 'production' && 'serviceWorker' in navigator) {
28 // The URL constructor is available in all browsers that support SW.
29 const publicUrl = new URL(process.env.PUBLIC_URL, window.location.href);
30 if (publicUrl.origin !== window.location.origin) {
31 // Our service worker won't work if PUBLIC_URL is on a different origin
32 // from what our page is served on. This might happen if a CDN is used to
33 // serve assets; see https://github.com/facebook/create-react-app/issues/2374
34 return;
35 }
36
37 window.addEventListener('load', () => {
38 const swUrl = `${process.env.PUBLIC_URL}/service-worker.js`;
39
40 if (isLocalhost) {
41 // This is running on localhost. Let's check if a service worker still exists or not.
42 checkValidServiceWorker(swUrl, config);
43
44 // Add some additional logging to localhost, pointing developers to the
45 // service worker/PWA documentation.
46 navigator.serviceWorker.ready.then(() => {
47 console.log(
48 'This web app is being served cache-first by a service ' +
49 'worker. To learn more, visit https://bit.ly/CRA-PWA'
50 );
51 });
52 } else {
53 // Is not localhost. Just register service worker
54 registerValidSW(swUrl, config);
55 }
56 });
57 }
58}
59
60function registerValidSW(swUrl: string, config?: Config) {
61 navigator.serviceWorker
62 .register(swUrl)
63 .then((registration) => {
64 registration.onupdatefound = () => {
65 const installingWorker = registration.installing;
66 if (installingWorker === null) {
67 return;
68 }
69 installingWorker.onstatechange = () => {
70 if (installingWorker.state === 'installed') {
71 if (navigator.serviceWorker.controller) {
72 // At this point, the updated precached content has been fetched,
73 // but the previous service worker will still serve the older
74 // content until all client tabs are closed.
75 console.log(
76 'New content is available and will be used when all ' +
77 'tabs for this page are closed. See https://bit.ly/CRA-PWA.'
78 );
79
80 // Execute callback
81 if (config && config.onUpdate) {
82 config.onUpdate(registration);
83 }
84 } else {
85 // At this point, everything has been precached.
86 // It's the perfect time to display a
87 // "Content is cached for offline use." message.
88 console.log('Content is cached for offline use.');
89
90 // Execute callback
91 if (config && config.onSuccess) {
92 config.onSuccess(registration);
93 }
94 }
95 }
96 };
97 };
98 })
99 .catch((error) => {
100 console.error('Error during service worker registration:', error);
101 });
102}
103
104function checkValidServiceWorker(swUrl: string, config?: Config) {
105 // Check if the service worker can be found. If it can't reload the page.
106 fetch(swUrl, {
107 headers: { 'Service-Worker': 'script' },
108 })
109 .then((response) => {
110 // Ensure service worker exists, and that we really are getting a JS file.
111 const contentType = response.headers.get('content-type');
112 if (response.status === 404 || (contentType !== null && contentType.indexOf('javascript') === -1)) {
113 // No service worker found. Probably a different app. Reload the page.
114 navigator.serviceWorker.ready.then((registration) => {
115 registration.unregister().then(() => {
116 window.location.reload();
117 });
118 });
119 } else {
120 // Service worker found. Proceed as normal.
121 registerValidSW(swUrl, config);
122 }
123 })
124 .catch(() => {
125 console.log('No internet connection found. App is running in offline mode.');
126 });
127}
128
129export function unregister() {
130 if ('serviceWorker' in navigator) {
131 navigator.serviceWorker.ready
132 .then((registration) => {
133 registration.unregister();
134 })
135 .catch((error) => {
136 console.error(error.message);
137 });
138 }
139}