TicTacToe/src/App.js

import './App.css';
import { useState } from 'react';

function Square() {
  const [value, setValue] = useState(null);

  function handleClick() {
    setValue('X')
  }

  return ( 
    <button 
      className="square"
      onClick={handleClick}
    >  
      {value}
    </button>
  );
}

function App() {
  return (
  <>
  <div className="board-row">
    <Square />
    <Square />
    <Square />
  </div>
  <div className="board-row">
    <Square />
    <Square />
    <Square />
  </div>
  <div className="board-row">
    <Square />
    <Square />
    <Square />
  </div>
  </>
  );
}

export default App;