text: const darkModeClass = "dark-mode";
  const button = document.getElementById("mode-selector");
  const h1 = document.getElementById("page-title");
  const body = document.getElementsByTagName("body")[0];
  const footer = document.getElementsByTagName("footer")[0];
  
  function changeMode() {
    changeClasses();
    changeText();
  }
  
  function changeClasses() { 
    button.classList.toggle(darkModeClass);
    h1.classList.toggle(darkModeClass);
    body.classList.toggle(darkModeClass);
    footer.classList.toggle(darkModeClass);
  }
  
  function changeText() {
    const lightMode = "Donnie Mode";
    const darkMode = "Darko Mode";
    
    if(body.classList.contains(darkModeClass)) {
      button.innerHTML = lightMode;
      h1.innerHTML = darkMode + " ON";
      return;
    }
    button.innerHTML = darkMode;
    h1.innerHTML = lightMode + " ON";
  }
  
  button.addEventListener('click', changeMode);