MediaWiki:Vector.js

$(window).on("load", function() {
    var isLightTheme = localStorage.getItem("isLightTheme");
    if (isLightTheme === "true") {
        document.documentElement.setAttribute('data-theme', 'light');
    } else {
        document.documentElement.setAttribute('data-theme', 'dark');
    }

    var button = document.createElement("button");
    button.innerHTML = "Сменить тему";
    button.className = "theme-button";
    button.onclick = toggleTheme;

    var container = document.getElementById("p-personal");
    if (container) {
        container.parentNode.insertBefore(button, container);
    }
});

function toggleTheme() {
    const root = document.documentElement;
    const currentTheme = root.getAttribute('data-theme');
    const newTheme = currentTheme === 'light' ? 'dark' : 'light';
    root.setAttribute('data-theme', newTheme);

    localStorage.setItem("isLightTheme", newTheme === 'light');
}