clean up

src/App.js

@@ -58,22 +58,20 @@ function Board({ xIsNext, squares, onPlay }) {
 }
 
 function App() {
-  const [xIsNext, setXIsNext] = useState(true);
   const [history, setHistory] = useState([Array(9).fill(null)]);
   const [currentMove, setCurrentMove] = useState(0);
+  const xIsNext = currentMove % 2 === 0;
   const currentSquares = history[currentMove];
 
   function handlePlay(nextSquares) {
     const nextHistory = [...history.slice(0, currentMove + 1), nextSquares];
     setHistory(nextHistory);
     setCurrentMove(nextHistory.length - 1);
-    setXIsNext(!xIsNext);
   }
 
   function jumpTo(nextMove) {
     setCurrentMove(nextMove);
     setHistory(history.slice(0, nextMove+1));
-    setXIsNext(nextMove % 2 === 0);
   }
 
   const moves = history.map((squares, move) => {