1 | // In production, we register a service worker to serve assets from local cache.
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2 |
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3 | // This lets the app load faster on subsequent visits in production, and gives
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4 | // it offline capabilities. However, it also means that developers (and users)
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5 | // will only see deployed updates on the "N+1" visit to a page, since previously
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6 | // cached resources are updated in the background.
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7 |
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8 | // To learn more about the benefits of this model, read https://goo.gl/KwvDNy.
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9 | // This link also includes instructions on opting out of this behavior.
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10 |
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11 | const isLocalhost = Boolean(
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12 | window.location.hostname === 'localhost' ||
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13 | // [::1] is the IPv6 localhost address.
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14 | window.location.hostname === '[::1]' ||
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15 | // 127.0.0.1/8 is considered localhost for IPv4.
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16 | window.location.hostname.match(
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17 | /^127(?:\.(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)){3}$/
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18 | )
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19 | );
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20 |
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21 | export function register(config) {
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22 | if (process.env.NODE_ENV === 'production' && 'serviceWorker' in navigator) {
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23 | // The URL constructor is available in all browsers that support SW.
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24 | const publicUrl = new URL(process.env.PUBLIC_URL, window.location);
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25 | if (publicUrl.origin !== window.location.origin) {
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26 | // Our service worker won't work if PUBLIC_URL is on a different origin
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27 | // from what our page is served on. This might happen if a CDN is used to
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28 | // serve assets; see https://github.com/facebook/create-react-app/issues/2374
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29 | return;
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30 | }
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31 |
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32 | window.addEventListener('load', () => {
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33 | const swUrl = `${process.env.PUBLIC_URL}/service-worker.js`;
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34 |
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35 | if (isLocalhost) {
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36 | // This is running on localhost. Let's check if a service worker still exists or not.
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37 | checkValidServiceWorker(swUrl, config);
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38 |
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39 | // Add some additional logging to localhost, pointing developers to the
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40 | // service worker/PWA documentation.
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41 | navigator.serviceWorker.ready.then(() => {
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42 | console.log(
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43 | 'This web app is being served cache-first by a service ' +
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44 | 'worker. To learn more, visit https://goo.gl/SC7cgQ'
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45 | );
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46 | });
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47 | } else {
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48 | // Is not local host. Just register service worker
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49 | registerValidSW(swUrl, config);
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50 | }
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51 | });
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52 | }
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53 | }
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54 |
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55 | function registerValidSW(swUrl, config) {
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56 | navigator.serviceWorker
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57 | .register(swUrl)
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58 | .then(registration => {
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59 | registration.onupdatefound = () => {
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60 | const installingWorker = registration.installing;
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61 | installingWorker.onstatechange = () => {
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62 | if (installingWorker.state === 'installed') {
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63 | if (navigator.serviceWorker.controller) {
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64 | // At this point, the old content will have been purged and
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65 | // the fresh content will have been added to the cache.
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66 | // It's the perfect time to display a "New content is
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67 | // available; please refresh." message in your web app.
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68 | console.log('New content is available; please refresh.');
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69 |
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70 | // Execute callback
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71 | if (config.onUpdate) {
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72 | config.onUpdate(registration);
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73 | }
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74 | } else {
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75 | // At this point, everything has been precached.
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76 | // It's the perfect time to display a
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77 | // "Content is cached for offline use." message.
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78 | console.log('Content is cached for offline use.');
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79 |
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80 | // Execute callback
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81 | if (config.onSuccess) {
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82 | config.onSuccess(registration);
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83 | }
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84 | }
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85 | }
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86 | };
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87 | };
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88 | })
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89 | .catch(error => {
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90 | console.error('Error during service worker registration:', error);
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91 | });
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92 | }
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93 |
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94 | function checkValidServiceWorker(swUrl, config) {
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95 | // Check if the service worker can be found. If it can't reload the page.
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96 | fetch(swUrl)
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97 | .then(response => {
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98 | // Ensure service worker exists, and that we really are getting a JS file.
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99 | if (
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100 | response.status === 404 ||
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101 | response.headers.get('content-type').indexOf('javascript') === -1
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102 | ) {
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103 | // No service worker found. Probably a different app. Reload the page.
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104 | navigator.serviceWorker.ready.then(registration => {
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105 | registration.unregister().then(() => {
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106 | window.location.reload();
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107 | });
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108 | });
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109 | } else {
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110 | // Service worker found. Proceed as normal.
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111 | registerValidSW(swUrl, config);
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112 | }
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113 | })
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114 | .catch(() => {
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115 | console.log(
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116 | 'No internet connection found. App is running in offline mode.'
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117 | );
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118 | });
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119 | }
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120 |
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121 | export function unregister() {
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122 | if ('serviceWorker' in navigator) {
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123 | navigator.serviceWorker.ready.then(registration => {
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124 | registration.unregister();
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125 | });
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126 | }
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127 | }
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