Offline toast notifications

offline-notification.js

function showOfflineNotification() {
  if ('serviceWorker' in navigator) {
    // Open the cache and check if we have this page saved
    caches.open('beer-data').then(function(cache) {
      var urlToCheck = 'https://deanhume.github.io/beer' + createStyleUrl(styleId, pageId, false);
        cache.match(urlToCheck)
        .then(function(response) {
          if (response == undefined){ return; } // return if we found nothing
          // We found the resource in cache
          if (response.ok && localStorage.getItem(urlToCheck) === null) {
              var snackbarContainer = document.querySelector('#offline-notification');
              var data = {message: 'This page is now available offline'};
              snackbarContainer.MaterialSnackbar.showSnackbar(data);

              // Save the message into storage
              localStorage.setItem(urlToCheck, true);
          }
        });
    });
  }
}