125 | ))}
126 |
127 |
128 | );
129 | }
130 | }
131 |
132 | export default App;
133 |
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/src/App.test.js:
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1 | import React from 'react';
2 | import ReactDOM from 'react-dom';
3 | import App from './App';
4 |
5 | it('renders without crashing', () => {
6 | const div = document.createElement('div');
7 | ReactDOM.render(, div);
8 | ReactDOM.unmountComponentAtNode(div);
9 | });
10 |
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/src/index.css:
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1 | body {
2 | margin: 0;
3 | padding: 0;
4 | font-family: sans-serif;
5 | }
6 |
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/src/index.js:
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1 | import React from 'react';
2 | import ReactDOM from 'react-dom';
3 | import './index.css';
4 | import App from './App';
5 | import registerServiceWorker from './registerServiceWorker';
6 |
7 | ReactDOM.render(, document.getElementById('root'));
8 | registerServiceWorker();
9 |
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/src/registerServiceWorker.js:
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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 |
11 | const 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}$/
18 | )
19 | );
20 |
21 | export default function register() {
22 | if (process.env.NODE_ENV === 'production' && 'serviceWorker' in navigator) {
23 | // The URL constructor is available in all browsers that support SW.
24 | const publicUrl = new URL(process.env.PUBLIC_URL, window.location);
25 | if (publicUrl.origin !== window.location.origin) {
26 | // Our service worker won't work if PUBLIC_URL is on a different origin
27 | // from what our page is served on. This might happen if a CDN is used to
28 | // serve assets; see https://github.com/facebookincubator/create-react-app/issues/2374
29 | return;
30 | }
31 |
32 | window.addEventListener('load', () => {
33 | const swUrl = `${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 |
55 | function 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 |
84 | function 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 |
111 | export function unregister() {
112 | if ('serviceWorker' in navigator) {
113 | navigator.serviceWorker.ready.then(registration => {
114 | registration.unregister();
115 | });
116 | }
117 | }
118 |
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