Tampermonkey script to automatically toggle Light/Dark theme on J-Novel Club website

jnovelclub-auto-theme.user.js

// ==UserScript==
// @name         J-Novel Club Auto Theme
// @version      0.1
// @description  Automatically switches between light and dark themes on j-novel.club based on system settings.
// @author       13xforever
// @match        https://j-novel.club/*
// @run-at       document-idle
// @license MIT
// ==/UserScript==

(function() {
    "use strict";
    if (!window.matchMedia) {
        return;
    }

    const LIGHT = "Let there be light!";
    const DARK = "Lights out!";
    const currentThemeSelector = 'div.theme div.button-group div.disabled';
    const switchSelector = 'div.theme div.button-group div.type-text';

    function checkMode(q) {
        try {
            let currentNightMode = document.querySelector(currentThemeSelector).title;
            let newNightMode = q.matches ? DARK : LIGHT;
            if (newNightMode !== currentNightMode) {
                document.querySelector(switchSelector).click();
            }
        } catch (ex) {
            console.log(`Failed: ${ex}`);
        }
    }
    const query = window.matchMedia('(prefers-color-scheme: dark)');
    checkMode(query);
    query.addEventListener('change', checkMode);
})();