twitch-ad-mute.user.js

// ==UserScript==
// @name         Mute preroll ads on twitch
// @namespace    http://agartner.com
// @version      0.3
// @author       Alex Gartner
// @match        https://www.twitch.tv/*
// ==/UserScript==

let interval;
let didMute = false;

function set_player_blackout(shouldBlackout) {
    const player = document.querySelector('div.video-player > div > div > div > div:nth-child(1) > div');
    const color = shouldBlackout ? 'black': '';
    player.style.backgroundColor = color;
}

function set_mute(shouldMute) {
    const muteButton = document.querySelector('button[data-a-target="player-mute-unmute-button"]');
    const isCurrentlyMuted = muteButton.getAttribute('aria-label').includes('Unmute');
    if (shouldMute) {
        if (!isCurrentlyMuted) {
            muteButton.click()
            didMute = true;
            set_player_blackout(true);
        }

        // handle player already muted
        if (!didMute) {
            didMute = true;
            set_player_blackout(true);
        }
    } else {
        if (isCurrentlyMuted && didMute) {
            muteButton.click()
            didMute = false;
            set_player_blackout(false);
        }
    }
}

function loop() {
    const playerText = document.getElementsByClassName('video-player')[0].innerText;
    const adStatus = playerText.includes('ad break');
    set_mute(adStatus)
}

interval = setInterval(loop, 100);