import React, { useState, useEffect } from 'react';

​

const App = () => {

  const [darkMode, setDarkMode] = useState(false);

  useEffect(() => {

    const bodyElement = document.querySelector('body');

    if (darkMode) {

      bodyElement.classList.add('dark');

    } else {

      bodyElement.classList.remove('dark');

    }

  }, [darkMode]);

​

  const toggleDarkMode = () => {

    setDarkMode(!darkMode);

  };

​

  return (

    <div>

      <button onClick={toggleDarkMode}>

        {darkMode ? 'Disable Dark Mode' : 'Enable Dark Mode'}

      </button>

​

      {/* Your app content goes here */}

    </div>

  );

};

​

export default App;