change captions programmatically in Media Player (depending on lang attribute added to html element by Polylang)

footer-scripts.html

<script>

document.addEventListener("DOMContentLoaded", () => {

  const currentLang = document.documentElement.lang; 

  document.querySelectorAll(".brxe-xmediaplayer").forEach((player, index) => {

    player.addEventListener("loaded-metadata", () => {

      for (const track of player.textTracks) {
        const trackLang = track.language ? track.language.replace(/-auto$/, "") : "";

        if (trackLang && currentLang.startsWith(trackLang)) {
          track.mode = "showing";
        } else {
          track.mode = "disabled";
        }
      }

      player.textTracks.addEventListener("add", (event) => {
        const track = event.detail;
        const trackLang = track.language ? track.language.replace(/-auto$/, "") : "";

        if (trackLang && currentLang.startsWith(trackLang)) {
          track.mode = "showing";
        } else {
          track.mode = "disabled";
        }
      });
    });
  });
});

</script>