AudioTrackList

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 {{domxref("AudioTrack")}} object in the list.

Retrieve an instance of this object with {{domxref('HTMLMediaElement.audioTracks')}}. The individual tracks can be accessed using array syntax.

Instance properties

This interface also inherits properties from its parent interface, {{domxref("EventTarget")}}.

{{domxref("AudioTrackList.length", "length")}} {{ReadOnlyInline}}
- : The number of tracks in the list.

Instance methods

This interface also inherits methods from its parent interface, {{domxref("EventTarget")}}.

{{domxref("AudioTrackList.getTrackById", "getTrackById()")}}
- : Returns the {{domxref("AudioTrack")}} found within the AudioTrackList whose {{domxref("AudioTrack.id", "id")}} matches the specified string. If no match is found, null is returned.

Events

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.

Usage notes

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 {{domxref("AudioTrackList/addtrack_event", "addtrack")}} and {{domxref("AudioTrackList/removetrack_event", "removetrack")}} events, so that you can detect when tracks are added to or removed from the media element's stream. See the {{domxref("AudioTrackList/addtrack_event", "addtrack")}} and {{domxref("AudioTrackList/removetrack_event", "removetrack")}} events for details and examples.

Examples

Getting a media element's audio track list

To get a media element's AudioTrackList, use its {{domxref("HTMLMediaElement.audioTracks", "audioTracks")}} property.

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

Monitoring track count changes

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 {{domxref("AudioTrackList/addtrack_event", "addtrack")}} and {{domxref("AudioTrackList/removetrack_event", "removetrack")}} events are set up.

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

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