TextTrackList

Baseline Widely available

This feature is well established and works across many devices and browser versions. It’s been available across browsers since ⁨July 2015⁩.

TheTextTrackList interface is used to represent a list of the text tracks defined for the associated video or audio element, with each track represented by a separateTextTrack object in the list.

Text tracks can be added to a media element declaratively using the<track> element or programmatically using theHTMLMediaElement.addTextTrack() method.

An instance of this object can be retrieved using thetextTracks property of anHTMLMediaElement object.

For a givenHTMLMediaElement objectmedia, the individual tracks can be accessed using:

media.TextTracks[n], to get the n-th text track from the object's list of text tracks
themedia.textTracks.getTrackById() method

Instance properties

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

lengthRead only: The number of tracks in the list.

Instance methods

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

getTrackById(): Returns theTextTrack found within theTextTrackList whoseid matches the specified string. If no match is found,null is returned.

Events

addtrack: Fired when a new text track has been added to the media element.Also available via theonaddtrack property.
change: Fired when a text track has been made active or inactive.Also available via theonchange property.
removetrack: Fired when a new text track has been removed from the media element.Also available via theonremovetrack property.

In addition to being able to obtain direct access to the text tracks present on a media element,TextTrackList lets you set event handlers on theaddtrack andremovetrack events, so that you can detect when tracks are added to or removed from the media element's stream.

Examples

Getting a video element's text track list

To get a media element'sTextTrackList, use itstextTracks property.

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

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 theaddtrack andremovetrack events are set up.

textTracks.onaddtrack = updateTrackCount;textTracks.onremovetrack = updateTrackCount;function updateTrackCount(event) {  trackCount = textTracks.length;  drawTrackCountIndicator(trackCount);}