The addtrack event is fired when a track is added to a TextTrackList.

Use the event name in methods like addEventListener(), or set an event handler property.

addEventListener("addtrack", (event) => {});

onaddtrack = (event) => {};

A TrackEvent. Inherits from Event.

In addition to the properties listed below, properties from the parent interface, Event, are available.

track Read only

The TextTrack object to which the event refers.

Using addEventListener():

const mediaElement = document.querySelector("video, audio");

mediaElement.textTracks.addEventListener("addtrack", (event) => {
  console.log(`Text track: ${event.track.label} added`);
});

Using the onaddtrack event handler property:

const mediaElement = document.querySelector("video, audio");

mediaElement.textTracks.onaddtrack = (event) => {
  console.log(`Text track: ${event.track.label} added`);
};

• Related events: removetrack, change
• This event on VideoTrackList targets: addtrack
• This event on AudioTrackList targets: addtrack
• This event on MediaStream targets: addtrack
• Media Capture and Streams API
• WebRTC