The MediaStream.getTrackById() method returns a MediaStreamTrack object representing the track with the specified ID string. If there is no track with the specified ID, this method returns null.

id

A string which identifies the track to be returned.

If a track is found for which MediaStreamTrack.id matches the specified id string, that MediaStreamTrack object is returned. Otherwise, the returned value is null.

This example activates a commentary track on a video by ducking the audio level of the main audio track to 50%, then enabling the commentary track.

stream.getTrackById("primary-audio-track").applyConstraints({ volume: 0.5 });
stream.getTrackById("commentary-track").enabled = true;

• MediaStream
• MediaStreamTrack.id