React Learning : Convert Tutorial into one with Hooks

tictactoe-hooks.js

function Square(props) {
  return (
    <button className="square" onClick={props.onClick}>
      {props.value}
     </button>
  )
}

function Board(props) {
  function renderSquare(i) {
    return <Square 
             value={props.squares[i]}
             onClick={() => props.onClick(i)}
             />;
  }

  return (
      <div>
        <div className="board-row">
          {renderSquare(0)}
          {renderSquare(1)}
          {renderSquare(2)}
        </div>
        <div className="board-row">
          {renderSquare(3)}
          {renderSquare(4)}
          {renderSquare(5)}
        </div>
        <div className="board-row">
          {renderSquare(6)}
          {renderSquare(7)}
          {renderSquare(8)}
        </div>
      </div>
    );
}

// With learnings from https://github.com/codeSTACKr/react-tic-tac-toe-hooks/blob/master/src/components/Game.js
function Game (props) {
  const [history, setHistory] = React.useState([Array(9).fill(null)]);
  const [stepNumber, setStepNumber] = React.useState(0);
  const [xIsNext, setXIsNext] = React.useState(true);
  
  //move these up here to avoid computation of winner 2x
  const current = history[stepNumber];
  const winner = calcWinner(current);
  
  function jumpTo(step) {
    setStepNumber(step);
    setXIsNext(step % 2 === 0);
  }
  
  function handleClick(i) {
    const historyPoint = history.slice(0, stepNumber + 1);
    const current = historyPoint[historyPoint.length - 1];
    // OR use the same: const current = historyPoint[stepNumber];
    const sq = current.slice();
    
    if (winner || sq[i]) {
      return;
    }
    sq[i] = xIsNext ? 'X' : 'O';
    // This breaks --> setHistory(historyPoint.concat(sq)); even if adding []
    setHistory([...historyPoint, sq]);
    
    //history.length is wrong, will go out of bounds
    setStepNumber(historyPoint.length);
    setXIsNext(!xIsNext);
  }
  
  const moves = history.map((step, move) => {
      const desc = move ? 'Go to move # ' + move
                        : 'Go to game start';
      return (
        <li key={move}>
          <button onClick={ () => jumpTo(move) }>{desc} </button>
         </li>
      )
    })
    
    const status = 'Next player: ' + (xIsNext ? 'X' : 'O');

    return (
      <div className="game">
        <div className="game-board">
          <Board squares={current}
                 onClick={(i) => handleClick(i)}/>
        </div>
        <div className="game-info">
          <div>{winner ? '!!! Winner:' + winner : status}</div>
          <ol>{moves}</ol>
        </div>
      </div>
    );
}

// ========================================

const root = ReactDOM.createRoot(document.getElementById("root"));
root.render(<Game />);


function calcWinner(squares) {
  const winningLines = [
    [0, 1, 2],
    [3, 4, 5],
    [6, 7, 8],
    [0, 3, 6],
    [1, 4, 7],
    [2, 5, 8],
    [0, 4, 8],
    [2, 4, 6],
  ];
  for (let i = 0; i < winningLines.length; i++) {
    const [a,b,c] = winningLines[i];
    if (squares[a] && squares[a] === squares[b] && squares[a] === squares[c]) {
      return squares[a];
    }
  }
  return null;
}