This example includes an HTML button that, when clicked, triggers the request for notification permission using the Notification.requestPermission() method. The method returns a promise that resolves to the user's choice, which can be 'granted', 'denied', or 'default'. Depending on the user's response, the appropriate alert message will be shown. If permission is granted, you can proceed to send notifications to the user. If permission is denied, you won't be able to send notifications. Remember that PWAs need to be served over HTTPS to use the Notification API and other features related to service workers. Also, make sure to handle the asynchronous nature of the Notification API properly in your real-world applications.