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.
The TextTrackList 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 separate TextTrack object in the list.
Text tracks can be added to a media element declaratively using the <track> element or programmatically using the HTMLMediaElement.addTextTrack() method.
An instance of this object can be retrieved using the textTracks property of an HTMLMediaElement object.
For a given HTMLMediaElement object media, 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- the
media.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 the
TextTrackfound within theTextTrackListwhoseidmatches the specified string. If no match is found,nullis returned.
Events
addtrack-
Fired when a new text track has been added to the media element. Also available via the
onaddtrackproperty. change-
Fired when a text track has been made active or inactive. Also available via the
onchangeproperty. removetrack-
Fired when a new text track has been removed from the media element. Also available via the
onremovetrackproperty.
Usage notes
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 the addtrack and removetrack 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's TextTrackList, use its textTracks 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 the addtrack and removetrack events are set up.
textTracks.onaddtrack = updateTrackCount;
textTracks.onremovetrack = updateTrackCount;
function updateTrackCount(event) {
trackCount = textTracks.length;
drawTrackCountIndicator(trackCount);
}
Specifications
| Specification |
|---|
| HTML # text-track-api |
Browser compatibility
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