storageManager.js

// if user accepts, this will give `persistent` (true/false, 1/0) back to the promise itself

if (navigator.storage && navigator.storage.persist) {
  navigator.storage.persist().then((persistent) => {
    if (persistent) {
      // let the user know about what will happen 
      "Great! You will never loose your data even after clearing the cache of your browser."
    } else {
      "Ups, you need to activate storage within your browser to get notified."
    }
  });
}