The data read-only property of the Notification interface returns a structured clone of the notification's data, as specified in the data option of the Notification() constructor.

The notification's data can be any arbitrary data that you want associated with the notification.

A structured clone.

The following snippet fires a notification; a simple options object is created, then the notification is fired using the Notification() constructor.

const options = {
  body: "Your code submission has received 3 new review comments.",
  data: {
    url: "https://example.com/review/12345",
    status: "open",
  },
};

const n = new Notification("New review activity", options);

console.log(n.data); // Logs the data object

• Using the Notifications API