gistfile1.txt

// ==UserScript==
// @name         Show Youtube Dislike Count
// @namespace    maxhyt.youtubepp
// @version      1.1.2.1
// @description  (Re)Add dislike count to YouTube videos
// @author       Maxhyt
// @license      AGPL-3.0
// @match        https://www.youtube.com/*
// @icon         https://icons.duckduckgo.com/ip2/youtube.com.ico
// @grant        none
// @run-at       document-idle
// ==/UserScript==

(async function() {
    'use strict';

    while (document.body.querySelector('ytd-sentiment-bar-renderer') === null) {
        await Sleep(100);
    }

    let likeBarContainer = document.body.querySelector('ytd-sentiment-bar-renderer');
    let tooltip = likeBarContainer.querySelector('#tooltip');

    likeBarContainer.querySelector('#container').addEventListener('mouseover', () => {
        tooltip.classList.remove('hidden');
    });
    likeBarContainer.querySelector('#container').addEventListener('mouseleave', () => {
        tooltip.classList.add('hidden');
    });

    window.addEventListener('yt-page-data-updated', UpdateCounter);

    const buttons = document.body.querySelectorAll('a.yt-simple-endpoint > yt-formatted-string.ytd-toggle-button-renderer');
    let likeText = buttons[0];
    let dislikeText = buttons[1];

    function UpdateCounter() {
        const data = document.querySelector("ytd-app")?.data;
        const contents = data?.response.contents.twoColumnWatchNextResults?.results.results.contents;
        
        if (data && contents) {
            let videoInfo;
            
            for (const content of contents) {
                if (content.videoPrimaryInfoRenderer) {
                    videoInfo = content.videoPrimaryInfoRenderer;
                    break;
                }
            }
            
            const likeCount = parseInt(videoInfo?.videoActions.menuRenderer.topLevelButtons[0].toggleButtonRenderer.accessibility.label.replace(/\D/g, ''));

            if (likeCount >= 0) {
                const r = data.playerResponse.videoDetails.averageRating;
                const dislikeCount = Math.round(likeCount * (5 - r) / (r - 1));
                
                ShowDislikes(likeCount, dislikeCount);
            }
        }
    }

    function ShowDislikes(likeCount, dislikeCount) {
        dislikeText.innerHTML = formatNumber(dislikeCount);

        if (likeBarContainer) {
            const likeBarWidth = likeText.parentNode.parentNode.getBoundingClientRect().width + dislikeText.parentNode.parentNode.getBoundingClientRect().width + 8;
            likeBarContainer.style.width = `${likeBarWidth}px`;
            likeBarContainer.removeAttribute('hidden');
            
            const likePerc = Math.floor(likeCount / (likeCount + dislikeCount) * 100);

            likeBarContainer.querySelector('#like-bar').style.width = `${likePerc}%`;
            tooltip.innerHTML = `${likeCount.toLocaleString()} / ${dislikeCount.toLocaleString()}`;
        }
    }

    function formatNumber(num) {
        if (num >= 1e9) {
            const tmp = num >= 1e10 ? Math.floor(num / 1e9) : (Math.floor(num / 1e8) / 10);
            return `${tmp.toLocaleString()}B`;
        }
        if (num >= 1e6) {
            const tmp = num >= 1e7 ? Math.floor(num / 1e6) : (Math.floor(num / 1e5) / 10);
            return `${tmp.toLocaleString()}M`;
        }
        if (num >= 1e3) {
            const tmp = num >= 1e4 ? Math.floor(num / 1e3) : (Math.floor(num / 1e2) / 10);
            return `${tmp.toLocaleString()}K`;
        }
        
        return num;
    }
    
    function Sleep(timeout) {
        return new Promise(resolve => {
            setTimeout(() => resolve(), timeout);
        });
    }

    UpdateCounter();
})();

Script not recognized as compatible with Tampermonkey 4.13.6136 (1 May 2021). Mozilla Firefox 98.0 (64-bit).