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 export default function register() {

    12   if (process.env.NODE_ENV === 'production' && 'serviceWorker' in navigator) {

    13     window.addEventListener('load', () => {

    14       const swUrl = `${process.env.PUBLIC_URL}/service-worker.js`;

    15       navigator.serviceWorker

    16         .register(swUrl)

    17         .then(registration => {

    18           registration.onupdatefound = () => {

    19             const installingWorker = registration.installing;

    20             installingWorker.onstatechange = () => {

    21               if (installingWorker.state === 'installed') {

    22                 if (navigator.serviceWorker.controller) {

    23                   // At this point, the old content will have been purged and

    24                   // the fresh content will have been added to the cache.

    25                   // It's the perfect time to display a "New content is

    26                   // available; please refresh." message in your web app.

    27                   console.log('New content is available; please refresh.');

    28                 } else {

    29                   // At this point, everything has been precached.

    30                   // It's the perfect time to display a

    31                   // "Content is cached for offline use." message.

    32                   console.log('Content is cached for offline use.');

    33                 }

    34               }

    35             };

    36           };

    37         })

    38         .catch(error => {

    39           console.error('Error during service worker registration:', error);

    40         });

    41     });

    42   }

    43 }

    44 

    45 export function unregister() {

    46   if ('serviceWorker' in navigator) {

    47     navigator.serviceWorker.ready.then(registration => {

    48       registration.unregister();

    49     });

    50   }

    51 }