Youtube emoji fix

yt-emoji.user.js

// ==UserScript==
// @name         Youtube emoji fix
// @namespace    youtube.emoji.fix
// @version      0.1
// @description  Improved Youtube chat performance by replacing SVG emoji to PNG file.
// @author       PokeGuys
// @match        *://www.youtube.com/live_chat*
// @run-at       document-start
// @grant        none
// ==/UserScript==

(function() {
    'use strict';

    // YT_EMOJI_CONFIG_URL represents the URL of youtube emoji list.
    const YT_EMOJI_CONFIG_URL = 'https://www.gstatic.com/youtube/img/emojis/emojis-svg-5.json';

    // DISABLE_EMOJI_KEYBOARD indicate that emoji is disabled in emoji keyboard.
    const DISABLE_EMOJI_KEYBOARD = false;

    /**
     * Apply emoji patch.
     *
     * @param rawEmojiList  The raw emoji list in Text format.
     * @returns Patched emoji list
     */
    const applyPatch = (rawEmojiList) => {
        // Early exit when `DISABLE_EMOJI_KEYBOARD` is true.
        if (DISABLE_EMOJI_KEYBOARD) {
            return '[]';
        }
        // Replace `.svg` to `.png`.
        return rawEmojiList.replace(/\.svg/, '.png')
    };

    // Hook `XMLHttpRequest.open` function to inject our patched code.
    const originalOpen = XMLHttpRequest.prototype.open;
    XMLHttpRequest.prototype.open = function() {
        this.addEventListener('load', function() {
            // Only affect URL match `YT_EMOJI_CONFIG_URL`
            if (this.responseURL.includes(YT_EMOJI_CONFIG_URL)) {
                const patchedResponse = applyPatch(this.responseText);
                // Dirty hack to modify readonly properties `response`, `responseText`.
                Object.defineProperty(this, 'response', {writable: true});
                Object.defineProperty(this, 'responseText', {writable: true});
                this.response = this.responseText = patchedResponse;
                // Release `XMLHttpRequest.open` hook.
                XMLHttpRequest.prototype.open = originalOpen;
            }
        });
        // Invoke original `open()` function.
        originalOpen.apply(this, arguments);
    };
})();