The id property contains a string which uniquely identifies the track represented by the AudioTrack.
This ID can be used with the AudioTrackList.getTrackById() method to locate a specific track within the media associated with a media element. The track ID can also be used as the fragment of a URL that loads the specific track (if the media supports media fragments).
A string which identifies the track, suitable for use when calling getTrackById() on an AudioTrackList such as the one specified by a media element's audioTracks property.