MediaWiki:Vector.js

// Кнопочка для переключения темы на светлую и обратно.
function createThemeToggleButton() {
  var container = document.getElementById("p-personal");
  if (container) {
      var checkbox = document.createElement("input");
      checkbox.type = "checkbox";
      checkbox.id = "theme-toggle";

      var label = document.createElement("label");
      label.htmlFor = "theme-toggle";
      label.id = "theme-button";

      container.parentNode.insertBefore(checkbox, container);
      container.parentNode.insertBefore(label, container);
  }

  var isLightTheme = localStorage.getItem("isLightTheme");
  if (isLightTheme === "true") {
      document.documentElement.classList.add('light');
  } else {
      document.documentElement.classList.remove('light');
  }

  $("#theme-toggle").change(function() {
      toggleTheme();
  });
}

function toggleTheme() {
  var isLightTheme = document.documentElement.classList.toggle('light');
  localStorage.setItem("isLightTheme", isLightTheme);
}

createThemeToggleButton();