MediaStream: getTrackById() method

{{APIRef("Media Capture and Streams")}}

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

Syntax

getTrackById(id)

Parameters

• id
  • : A string which identifies the track to be returned.

Return value

If a track is found for which {{domxref("MediaStreamTrack.id")}} matches the specified id string, that {{domxref("MediaStreamTrack")}} object is returned. Otherwise, the returned value is null.

Examples

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.

The example assumes that the IDs of the two tracks are known (for example, from a previous call to {{domxref("MediaStreamTrack.id")}}). In a real application, you might store these IDs when you first obtain the stream, because they are randomly generated in the browser.

const primaryAudioTrack = stream.getTrackById(
  "69f8520f-d94e-43f0-8a7c-77b1774f3b8f",
);
const commentaryTrack = stream.getTrackById(
  "b5410643-2549-491e-b0f7-f08a4ebe54b8",
);

primaryAudioTrack.applyConstraints({ volume: 0.5 });
commentaryTrack.enabled = true;

Specifications

{{Specifications}}

Browser compatibility

{{Compat}}

See also

• {{domxref("MediaStream")}}
• {{domxref("MediaStreamTrack.id")}}