The AudioTrackList interface is used to represent a list of the audio tracks contained within a given HTML media element, with each track represented by a separate AudioTrack object in the list.

Retrieve an instance of this object with HTMLMediaElement.audioTracks. The individual tracks can be accessed using array syntax.

This interface also inherits properties from its parent interface, EventTarget.

length Read only

The number of tracks in the list.

This interface also inherits methods from its parent interface, EventTarget.

getTrackById()

Returns the AudioTrack found within the AudioTrackList whose id matches the specified string. If no match is found, null is returned.

addtrack

Fired when a new audio track has been added to the media element.

change

Fired when a track has been enabled or disabled.

removetrack

Fired when a new audio track has been removed from the media element.

In addition to being able to obtain direct access to the audio tracks present on a media element, AudioTrackList lets you set event handlers on the addtrack and removetrack events, so that you can detect when tracks are added to or removed from the media element's stream. See the addtrack and removetrack events for details and examples.

To get a media element's AudioTrackList, use its audioTracks property.

const audioTracks = document.querySelector("video").audioTracks;

In this example, we have an app that displays information about the number of channels available. To keep it up to date, handlers for the addtrack and removetrack events are set up.

audioTracks.onaddtrack = updateTrackCount;
audioTracks.onremovetrack = updateTrackCount;

function updateTrackCount(event) {
  trackCount = audioTracks.length;
  drawTrackCountIndicator(trackCount);
}