document.addEventListener('DOMContentLoaded', initPage, false);
  function initPage() {
    if (!('Notification' in window)) {
      // this browser does not support notifications
    } else if (Notification.permission === 'denied') {
      // the user denied notification permission!
    else if (Notification.permission === 'granted') {
      pirateManager.subscribeToPush();
} ...
function enableNotifications() {
  Notification.requestPermission().then((result) => {
    pirateManager.subscribeToPush();
  });
}