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YouTube autolike

Auto-like YouTube video if you are subscribed to the author's channel.

As of 2021-03-24. See the latest version.

// ==UserScript==
// @name         YouTube autolike
// @namespace    https://github.com/blackstar0169/youtube-autolike-script
// @version      1.1
// @description  Auto-like YouTube video if you are subscribed to the author's channel.
// @author       blackstar0169
// @match        https://www.youtube.com/watch*
// @grant        none
// ==/UserScript==

(function() {
    'use strict';

    var watcher = null;
    var likeSelector = '#info-contents #top-level-buttons > ytd-toggle-button-renderer > a';
    var subscribeSelector = '.ytd-subscribe-button-renderer';

    // Check if the video is already liked
    function isLiked() {
        var likeBtn = document.querySelector(likeSelector);
        return likeBtn ? likeBtn.querySelector(':scope > .style-default-active') != null : false;
    }

    function autoLike() {
        var subscribeBtn = document.querySelector(subscribeSelector + '[subscribed]');

        // If the button exsits, the user is subscribed to this channel
        if (subscribeBtn) {
            var likeBtn = document.querySelector(likeSelector);

            if (likeBtn && !isLiked()) {
                likeBtn.click();
                return true;
            }
        }

        return false;
    }

    // Watch untile the like button has or has been pressed
    function startWatcher() {
        watcher = setInterval(function () {
            if (document.querySelector(subscribeSelector)) {
                if (isLiked() || autoLike()) {
                    clearInterval(watcher);
                }
            }
        }, 1000);
    }

    // Wait for the interface load event
    window.addEventListener("yt-navigate-finish", startWatcher, true)
})();