YouTube - Player Undo Button

youtube-player-undo-button.user.js

// ==UserScript==
// @name            YouTube - Player Undo Button
// @description     Adds an undo button to the player controls, which undoes the last skip action.
// @version         0.0.2
// @author          aequabit
// @match           https://www.youtube.com/watch*
// @run-at          document-start
// @downloadURL     https://gist.github.com/aequabit/39c3150dcd31dcb6c92aff8024e8cfba/raw/youtube-player-undo-button.user.js
// ==/UserScript==

// Mostly taken from https://chromewebstore.google.com/detail/youtube-undo/jdoinlndbffpmioacnkpkjdbcphpembi

(async () => {
    const state = {
        savedTime: 0,
        skipTo: null
    };


    const btnUndo = document.createElement("button");
    btnUndo.classList.add("ytp-button");
    btnUndo.id = "ytp-button-undo";

    // https://fonts.google.com/icons?selected=Material%20Symbols%20Outlined%3Aundo%3AFILL%400%3Bwght%40400%3BGRAD%400%3Bopsz%4024&icon.query=undo&icon.size=24&icon.color=%23e3e3e3
    btnUndo.innerHTML = `
        <svg height="100%" viewBox="0 0 36 36" width="100%">
            <path d="m 13.368712,25 v -1.866666 h 6.576429 q 1.458856,0 2.535631,-0.933333 1.076774,-0.933334 1.076774,-2.333334 0,-1.4 -1.076774,-2.333333 -1.076775,-0.933333 -2.535631,-0.933333 h -5.835423 l 2.40827,2.426666 -1.296761,1.306666 L 10.589938,15.666667 15.221227,11 l 1.296761,1.306666 -2.40827,2.426667 h 5.835423 q 2.246175,0 3.855548,1.47 1.609373,1.470001 1.609373,3.663334 0,2.193334 -1.609373,3.663333 Q 22.191316,25 19.945141,25 Z" id="path1" style="stroke-width:0.0232447;fill:#ffffff;fill-opacity:1" />
        </svg>
    `;

    btnUndo.addEventListener("click", _ => {
        if (state.skipTo !== null)
            document.getElementsByTagName('video')[0].currentTime = state.skipTo;
    })

    setInterval(() => {
        if (document.querySelector(".ytp-right-controls") && !document.querySelector("#ytp-button-undo"))
            document.querySelector(".ytp-right-controls").prepend(btnUndo);

        if (document.getElementsByTagName('video').length > 0) {
            const playTime = document.getElementsByTagName('video')[0].currentTime;

            if (playTime > state.savedTime + 10 || playTime < state.savedTime - 10)
                state.skipTo = state.savedTime;

            state.savedTime = playTime - 1;
        }
    }, 1000)
})();