VideoTrackList
The VideoTrackList
interface is used to represent a list of the video tracks contained within a <video>
element, with each track represented by a separate VideoTrack
object in the list.
Retrieve an instance of this object with HTMLMediaElement.videoTracks
. The individual tracks can be accessed using array syntax or functions such as forEach()
for example.
Instance properties
This interface also inherits properties from its parent interface, EventTarget
.
length
Read only-
The number of tracks in the list.
selectedIndex
Read only-
The index of the currently selected track, if any, or
−1
otherwise.
Instance methods
This interface also inherits methods from its parent interface, EventTarget
.
getTrackById()
-
Returns the
VideoTrack
found within theVideoTrackList
whoseid
matches the specified string. If no match is found,null
is returned.
Events
addtrack
-
Fired when a new video track has been added to the media element. Also available via the
onaddtrack
property. change
-
Fired when a video track has been made active or inactive. Also available via the
onchange
property. removetrack
-
Fired when a new video track has been removed from the media element. Also available via the
onremovetrack
property.
Usage notes
In addition to being able to obtain direct access to the video tracks present on a media element, VideoTrackList
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 media element's video track list
To get a media element's VideoTrackList
, use its videoTracks
property.
js
const videoTracks = document.querySelector("video").videoTracks;
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.
js
videoTracks.onaddtrack = updateTrackCount;
videoTracks.onremovetrack = updateTrackCount;
function updateTrackCount(event) {
trackCount = videoTracks.length;
drawTrackCountIndicator(trackCount);
}
Specifications
Specification |
---|
HTML Standard # audiotracklist-and-videotracklist-objects |
Browser compatibility
BCD tables only load in the browser