(YouTube) DVRでズレている時にメッセージを表示

bookmarklet_yt_show_lag_message.js

javascript:(()=>{
const eVideo = document.querySelector('video.video-stream');
const eProgressBar = document.querySelector('.ytp-progress-bar');

const eMessage = document.createElement('div');
eMessage.style.cssText = 'color: red; font-size: 16px;';
const eContainer = document.querySelector('#chat-container');
eContainer.parentNode.insertBefore(eMessage, eContainer.nextSibling);

const makeLagMessage = (s) => `リアルタイムから${s}秒ズレています。`;
const handler = () => {
    const now = parseInt(eProgressBar.getAttribute('aria-valuenow'));
    const max = parseInt(eProgressBar.getAttribute('aria-valuemax'));
    const eps = 5;
    const delta = Math.abs(max - now);
    eMessage.textContent = (delta > eps) ? makeLagMessage(delta) : '';
};

eVideo.addEventListener('play', handler);
eVideo.addEventListener('seeked', handler);
eVideo.addEventListener('timeupdate', handler);
})();