koer2x.user.js

// ==UserScript==
// @name         koer2x
// @namespace    https://gist.github.com/tnRaro/aa2a08e3e6c12a3107381aeda2696779/raw/koer2x.user.js
// @version      0.3
// @description  try to take over the world!
// @author       tnRaro
// @match        http://www.koer.kr/*
// @match        http://www.udec.kr/*
// @grant        none
// ==/UserScript==

globalThis.api = {
  setPlaybackRate(speed = 2) { document.getElementById("my-video_html5_api").playbackRate = speed; }
};

(function() {
    'use strict';

    window.onload = () => {
        globalThis.api.setPlaybackRate();
    }
})();