Get YouTube Playlist total time

main.js

//@ts-check
console.time('Elapsed time');
const playlistVideos = document.querySelector(
  "#contents > ytd-playlist-video-list-renderer > #contents"
);
const spanTime = document.querySelectorAll(
  "#overlays > ytd-thumbnail-overlay-time-status-renderer > span"
);
let playlistTime = 0;
for (let i = 0; i < playlistVideos.childElementCount; i++) {
  const videoTime = humanTimeToSeconds(spanTime[i].textContent.trim());
  playlistTime += videoTime;
}

// output
console.log(`Total Time: ${secondsToHumanTime(playlistTime)}`);
console.timeEnd("Elapsed time");

/**
 * Convert Human Time to seconds
 * @param {String} time the input human time
 * @returns {Number}
 */
function humanTimeToSeconds(time) {
  let totalTime = 0;
  const parts = time.split(":");
  if (parts.length > 2) {
    totalTime =
      parseInt(parts[0]) * 60 * 60 +
      parseInt(parts[1]) * 60 +
      parseInt(parts[2]);
  } else {
    totalTime = parseInt(parts[0]) * 60 + parseInt(parts[1]);
  }
  return totalTime;
}

/**
 * Convert Seconds to Human Time
 * @param {Number} seconds
 * @returns {String}
 */
function secondsToHumanTime(seconds) {
  const dump = new Date(null);
  dump.setSeconds(seconds);
  const isoDate = dump.toISOString();
  const dateParts = isoDate.split("T");
  return dateParts[1].replace(".000Z", "");
}