Service Workers & Progressive Web Apps

let deferredPrompt;

window.addEventListener('beforeinstallprompt', event => {
  event.preventDefault();
  deferredPrompt = event;
  showInstallButton();
});

installButton.addEventListener('click', () => {
  deferredPrompt.prompt();
  deferredPrompt.userChoice.then(choice => {
    if (choice.outcome === 'accepted') {
      console.log('PWA installed');
    }
    deferredPrompt = null;
  });
});