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(
 19      /^127(?:\.(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)){3}$/
 20    )
 21);
 22
 23export function register(config) {
 24  if (process.env.NODE_ENV === 'production' && 'serviceWorker' in navigator) {
 25    // The URL constructor is available in all browsers that support SW.
 26    const publicUrl = new URL(process.env.PUBLIC_URL, window.location.href);
 27    if (publicUrl.origin !== window.location.origin) {
 28      // Our service worker won't work if PUBLIC_URL is on a different origin
 29      // from what our page is served on. This might happen if a CDN is used to
 30      // serve assets; see https://github.com/facebook/create-react-app/issues/2374
 31      return;
 32    }
 33
 34    window.addEventListener('load', () => {
 35      const swUrl = `${process.env.PUBLIC_URL}/service-worker.js`;
 36
 37      if (isLocalhost) {
 38        // This is running on localhost. Let's check if a service worker still exists or not.
 39        checkValidServiceWorker(swUrl, config);
 40
 41        // Add some additional logging to localhost, pointing developers to the
 42        // service worker/PWA documentation.
 43        navigator.serviceWorker.ready.then(() => {
 44          console.log(
 45            'This web app is being served cache-first by a service ' +
 46              'worker. To learn more, visit https://bit.ly/CRA-PWA'
 47          );
 48        });
 49      } else {
 50        // Is not localhost. Just register service worker
 51        registerValidSW(swUrl, config);
 52      }
 53    });
 54  }
 55}
 56
 57function registerValidSW(swUrl, config) {
 58  navigator.serviceWorker
 59    .register(swUrl)
 60    .then(registration => {
 61      registration.onupdatefound = () => {
 62        const installingWorker = registration.installing;
 63        if (installingWorker == null) {
 64          return;
 65        }
 66        installingWorker.onstatechange = () => {
 67          if (installingWorker.state === 'installed') {
 68            if (navigator.serviceWorker.controller) {
 69              // At this point, the updated precached content has been fetched,
 70              // but the previous service worker will still serve the older
 71              // content until all client tabs are closed.
 72              console.log(
 73                'New content is available and will be used when all ' +
 74                  'tabs for this page are closed. See https://bit.ly/CRA-PWA.'
 75              );
 76
 77              // Execute callback
 78              if (config && config.onUpdate) {
 79                config.onUpdate(registration);
 80              }
 81            } else {
 82              // At this point, everything has been precached.
 83              // It's the perfect time to display a
 84              // "Content is cached for offline use." message.
 85              console.log('Content is cached for offline use.');
 86
 87              // Execute callback
 88              if (config && config.onSuccess) {
 89                config.onSuccess(registration);
 90              }
 91            }
 92          }
 93        };
 94      };
 95    })
 96    .catch(error => {
 97      console.error('Error during service worker registration:', error);
 98    });
 99}
100
101function checkValidServiceWorker(swUrl, config) {
102  // Check if the service worker can be found. If it can't reload the page.
103  fetch(swUrl, {
104    headers: {'Service-Worker': 'script'},
105  })
106    .then(response => {
107      // Ensure service worker exists, and that we really are getting a JS file.
108      const contentType = response.headers.get('content-type');
109      if (
110        response.status === 404 ||
111        (contentType != null && contentType.indexOf('javascript') === -1)
112      ) {
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(
126        'No internet connection found. App is running in offline mode.'
127      );
128    });
129}
130
131export function unregister() {
132  if ('serviceWorker' in navigator) {
133    navigator.serviceWorker.ready
134      .then(registration => {
135        registration.unregister();
136      })
137      .catch(error => {
138        console.error(error.message);
139      });
140  }
141}