The lang read-only property of the Notification interface indicates the language used in the notification, as specified in the lang option of the Notification() constructor.

The language itself is specified using a string representing a language tag according to RFC 5646: Tags for Identifying Languages (also known as BCP 47). See the Sitepoint ISO 2 letter language codes page for a simple reference.

A string specifying the language tag.

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.",
  lang: "en-US",
};

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

console.log(n.lang); // "en-US"

• Using the Notifications API