Calculates the time remaining until one finishes a playlist if they have been watching videos linearly in it

partial-youtube-playlist-time-calc.js

Array.from(document.querySelectorAll("ytd-playlist-video-renderer"))
  .slice(121) //Changes this number to the number of the last video you watched
  .map(x => x.querySelector(".ytd-thumbnail-overlay-time-status-renderer").textContent.trim())
  .reduce((acc, video) => {
    let [h, m, s] = video.split(":").map(x => parseInt(x));
    if (!s) {s = m; m = h; h = 0;}
    acc[0] += h;
    acc[1] += m;
    acc[2] += s;
    return acc;
  }, [0, 0, 0])
  .reduceRight((acc, clock, i) => {
    if (i > 0) {
      acc[i-1] = Math.floor((clock + acc[i]) / 60);
      acc[i] = (clock + acc[i]) % 60;
    } else {
      acc[i] += clock;
    }
    return acc;
  }, [0, 0, 0])
  .map(x => x.toString())
  .map(x => x.length >= 2 ? x : "0" + x)
  .join(":");
  

There's probably a more elegant way to write reduceRight's function (even if that way doesn't use reduceRight completely or changes the way the previous reduce works)