Changes the YouTube logo to a pumpkin

youtube_pumpkin_logo.user.js

// ==UserScript==
// @name         YouTube Pumpkin Logo
// @namespace    http://literalchaos.de
// @version      1.0
// @description  Changes the YouTube icon to a pumpkin
// @author       jangxx
// @match        https://www.youtube.com/*
// @grant        none
// @downloadURL  https://gist.github.com/jangxx/0fc73153c89194adbc6710eecab1b734/raw/youtube_pumpkin_logo.user.js
// @updateURL  https://gist.github.com/jangxx/0fc73153c89194adbc6710eecab1b734/raw/youtube_pumpkin_logo.user.js
// ==/UserScript==

const NEW_LOGO = "https://i.imgur.com/NxZY8tI.png";

function addLogo(parentSelector, replaceSelector) {
    const replaceElem = document.querySelector(replaceSelector);
    if (replaceElem == null) return;

    const parentElem = document.querySelector(parentSelector);
    if (parentElem == null) return;

    const size = replaceElem.getBoundingClientRect();
    const parentSize = parentElem.getBoundingClientRect();

    const logoImg = document.createElement("img");
    logoImg.src = NEW_LOGO;
    logoImg.width = size.width;
    logoImg.style.position = "absolute";
    logoImg.style.bottom = `${parentSize.bottom - size.bottom}px`;
    logoImg.style.left = `${-parentSize.left + size.left}px`;

    parentElem.appendChild(logoImg);

    replaceElem.remove();
}

function waitForNonNull(checkFn) {
    return new Promise(resolve => {
        let interval = setInterval(() => {
            let checkValue = checkFn();
            if (checkValue != null) {
                clearInterval(interval);
                resolve(checkValue);
            }
        }, 50);
    });
}

(function() {
    'use strict';

    document.querySelectorAll("link[rel='icon']").forEach(e => e.href= NEW_LOGO);
    document.querySelectorAll("link[rel='shortcut icon']").forEach(e => e.href= NEW_LOGO);

    waitForNonNull(() => document.querySelector("#logo-icon-container > svg > g > g:first-child")).then(() => {
        addLogo("#logo-red-icon-container", "#logo-red-icon-container > svg > g > g:first-child");
        addLogo("#logo-icon-container", "#logo-icon-container > svg > g > g:first-child");
    });
})();