User Script that forces original audio track on YouTube videos

force-original-youtube-audio-track.js

// ==UserScript==
// @name        Force original audio track on YouTube videos
// @match       https://youtube.com/*
// @match       https://www.youtube.com/*
// ==/UserScript==

const ORIGINAL_AUDIO_TRACK_NAME_PATTERN = /^.+?\([^\)]+\)\s+[^\(\)]+|.+?\s+original$/

new MutationObserver(debounce(100, update)).observe(document.head, {
  childList: true,
  subtree: true,
  characterData: true
})

setTimeout(update, 500)

function update() {
  for (const element of document.querySelectorAll('ytd-player')) {
    useOriginalAudioTrack(element.player_)
  }
}
  
function useOriginalAudioTrack(player) {
  const tracks = player.getAvailableAudioTracks()
  
  for (const track of tracks) {
    const { name } = track.getLanguageInfo()
    
    if (ORIGINAL_AUDIO_TRACK_NAME_PATTERN.test(name)) {
      player.setAudioTrack(track)
      break
    }
  }
}

function debounce(delay, callback) {
  let timeout

  return (...args) => {
    clearTimeout(timeout)
    timeout = setTimeout(callback, delay)
  }
}