The getCueById() method of the TextTrackCueList interface returns the first VTTCue in the list represented by the TextTrackCueList object whose identifier matches the value of id.

id

A string which is an identifier for the cue.

A VTTCue object.

The TextTrack.cues property returns a TextTrackCueList containing the current cues for that particular track. Calling cues.getCueById("second") returns the VTTCue with an ID of "second".

WEBVTT

first
00:00:00.000 --> 00:00:00.999 line:80%
Hildy!

second
00:00:01.000 --> 00:00:01.499 line:80%
How are you?

const video = document.getElementById("video");
video.onplay = () => {
  console.log(video.textTracks[0].cues.getCueById("second")); // a VTTCue object;
};