Loading and selecting subtitles

subtitles.js

let captionUrl = "http://amssamples.streaming.mediaservices.windows.net/bc57e088-27ec-44e0-ac20-a85ccbcd50da/TOS-en.vtt";
this.player
  .load(videoUrl)
  .then(() => {
    this.player.addTextTrackAsync(captionUrl, "en", "subtitle", 'text/vtt').then(() => {{
      const textTracks = this.player.getTextTracks();
      if (textTracks.length > 0) {
        this.player.setTextTrackVisibility(true);
        this.player.selectTextTrack(textTracks[0]);
      }
      this.videoElement?.play();
    }});
  })
  .catch((e: any) => {
    console.error(e);
  });