How do I display a message in a PWA when I’m offline?

How do I display an "Offline" message in a PWA ?

I created 1 post using Bootstrap 5 theme in my HTML code.

https://getbootstrap.com/docs/5.0/components/toasts/

What I want :

  • The message "You are offline" appears when the user has no internet connection?

How to do this ? Here is my code.

index.html

<!doctype html>
<html lang="fr" class="h-100">

  <head>
    <link rel="manifest" href="/manifest.json">
    <link rel="canonical" href="https://www.mathieulebert.fr/">
    <link href="bootstrap.min.css" rel="stylesheet">
    <link href="style.css" rel="stylesheet">
  </head>

  <body class="position-relative d-flex flex-column bg-dark text-white text-center" data-bs-spy="scroll" data-target="#navbar" data-bs-offset="85" tabindex="0">

      <div class="toast" role="alert" aria-live="assertive" aria-atomic="true">
        <div class="toast-header">
          <svg xmlns="http://www.w3.org/2000/svg" width="20" height="20" fill="currentColor" class="bi bi-wifi-off text-danger" viewBox="0 0 16 16">
            <path d="M10.706 3.294A12.545 12.545 0 0 0 8 3C5.259 3 2.723 3.882.663 5.379a.485.485 0 0 0-.048.736.518.518 0 0 0 .668.05A11.448 11.448 0 0 1 8 4c.63 0 1.249.05 1.852.148l.854-.854zM8 6c-1.905 0-3.68.56-5.166 1.526a.48.48 0 0 0-.063.745.525.525 0 0 0 .652.065 8.448 8.448 0 0 1 3.51-1.27L8 6zm2.596 1.404.785-.785c.63.24 1.227.545 1.785.907a.482.482 0 0 1 .063.745.525.525 0 0 1-.652.065 8.462 8.462 0 0 0-1.98-.932zM8 10l.933-.933a6.455 6.455 0 0 1 2.013.637c.285.145.326.524.1.75l-.015.015a.532.532 0 0 1-.611.09A5.478 5.478 0 0 0 8 10zm4.905-4.905.747-.747c.59.3 1.153.645 1.685 1.03a.485.485 0 0 1 .047.737.518.518 0 0 1-.668.05 11.493 11.493 0 0 0-1.811-1.07zM9.02 11.78c.238.14.236.464.04.66l-.707.706a.5.5 0 0 1-.707 0l-.707-.707c-.195-.195-.197-.518.04-.66A1.99 1.99 0 0 1 8 11.5c.374 0 .723.102 1.021.28zm4.355-9.905a.53.53 0 0 1 .75.75l-10.75 10.75a.53.53 0 0 1-.75-.75l10.75-10.75z"/>
          </svg>
          <strong class="me-auto">Vous êtes hors-ligne</strong>
          <button type="button" class="btn-close" data-bs-dismiss="toast" aria-label="Close"></button>
        </div>
        <div class="toast-body text-start text-dark">
          Les informations de cette page peuvent être obsolètes.
        </div>
      </div>
    </div>

    <script src="bootstrap.bundle.min.js"></script>
    <script src="popover.js"></script>
    <script src="clipboard.min.js"></script>
    <script src="btn-clipboard.js"></script>
    <script src="pwa.js"></script>
    <script src="feed.js"></script>

  </body>

</html>

pwa.js :

if ('serviceWorker' in navigator) {
  window.addEventListener('load', function() {
    navigator.serviceWorker.register('sw.js')
      .then(reg => {
        console.log('Service worker registered! 😎', reg);
      })
      .catch(err => {
        console.log('😥 Service worker registration failed: ', err);
      });
  });
}

sw.js :

const staticCacheName = 'v13';
const filesToCache = [
  '/',
  '/index.html',
  '/style.css',
  '/bootstrap.min.css',
  '/bootstrap.bundle.min.js',
  '/popover.js',
  '/clipboard.min.js',
  '/btn-clipboard.js',
  '/pwa.js',
  '/feed.js',
  '/icon-32.png',
  '/icon-144.png',
  '/icon-192.png',
  '/icon-512.png',
  '/iphone5_splash.png',
  '/iphone6_splash.png',
  '/iphoneplus_splash.png',
  '/iphonex_splash.png',
  '/iphonexr_splash.png',
  '/iphonexsmax_splash.png',
  '/ipad_splash.png',
  '/ipadpro1_splash.png',
  '/ipadpro3_splash.png',
  '/ipadpro2_splash.png'
];

self.addEventListener('install', event => {
  event.waitUntil(
    caches.open(staticCacheName).then(cache => {
      return cache.addAll(filesToCache);
    })
  );
});

self.addEventListener('activate', event => {
  event.waitUntil(caches.keys().then(function(cacheNames) {
    return Promise.all(
      cacheNames.filter(function(staticCacheName) {
      }).map(function(staticCacheName) {
        return caches.delete(staticCacheName);
      })
    );
  }));
});

self.addEventListener('fetch', event => {
  event.respondWith(caches.match(event.request).then(cachedResponse => {
    if (cachedResponse) {
      return cachedResponse;
    }
    return fetch(event.request);
  }));
});

self.addEventListener('message', event => {
  if (event.data.action === 'skipWaiting') {
    self.skipWaiting();
  }
});

Here are some examples :

enter image description here

Source: Ask Javascript Questions

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