The AudioTrackList method getTrackById() returns the first AudioTrack object from the track list whose id matches the specified string. This lets you find a specified track if you know its ID string.

id

A string indicating the ID of the track to locate within the track list.

An AudioTrack object indicating the first track found within the AudioTrackList whose id matches the specified string. If no match is found, this method returns null.

The tracks are searched in their natural order; that is, in the order defined by the media resource itself, or, if the resource doesn't define an order, the relative order in which the tracks are declared by the media resource.

This example suggests a hypothetical game in which movies are used as cut-scenes or other key set pieces within the game. Each movie has one audio track for each character, as well as one for the music, sound effects, and so forth. This function allows the game to disable a specific character's audio in order to adjust the movie's performance based on occurrences within the game; if the character's dialog isn't relevant, it gets left out. Obviously, that would require some clever graphic design to make work, but it's a hypothetical game.

function disableCharacter(videoElem, characterName) {
  videoElem.audioTracks.getTrackById(characterName).enabled = false;
}

This short function gets the AudioTrackList containing the video's audio tracks using HTMLMediaElement.audioTracks, then calls getTrackById() on it, specifying the character's name. The resulting track's audio is then disabled by setting its enabled flag to false.