Tic Tac Toe

index.html

<div id="errors" style="
  background: #c00;
  color: #fff;
  display: none;
  margin: -20px -20px 20px;
  padding: 20px;
  white-space: pre-wrap;
"></div>
<div id="root"></div>
<script>
window.addEventListener('mousedown', function(e) {
  document.body.classList.add('mouse-navigation');
  document.body.classList.remove('kbd-navigation');
});
window.addEventListener('keydown', function(e) {
  if (e.keyCode === 9) {
    document.body.classList.add('kbd-navigation');
    document.body.classList.remove('mouse-navigation');
  }
});
window.addEventListener('click', function(e) {
  if (e.target.tagName === 'A' && e.target.getAttribute('href') === '#') {
    e.preventDefault();
  }
});
window.onerror = function(message, source, line, col, error) {
  var text = error ? error.stack || error : message + ' (at ' + source + ':' + line + ':' + col + ')';
  errors.textContent += text + '\n';
  errors.style.display = '';
};
console.error = (function(old) {
  return function error() {
    errors.textContent += Array.prototype.slice.call(arguments).join(' ') + '\n';
    errors.style.display = '';
    old.apply(this, arguments);
  }
})(console.error);
</script>

script.babel

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

function calculateWinner(squares) {
    const lines = [
      [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 < lines.length; i++) {
      const [a, b, c] = lines[i];
      if (squares[a] && squares[a] === squares[b] && squares[a] === squares[c]) {
        return squares[a];
      }
    }
    return null;
  }

class Board extends React.Component {
  renderSquare(i) {
    return <Square value={this.props.squares[i]} onClick={() => this.props.onClick(i)}/>;
  }

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

const getBoard = (history, i) => {
  squares = Array(9).fill(null);
  for (let j = 0; j < i; j++) {
    squares[history[j]] = (j % 2 === 0) ? 'X' : 'O';
  }
  return squares;
};

class Game extends React.Component {
  
  constructor(props){
    super(props);
    this.history = [];
    this.state = {
      currentStep: 0,
    };
  }
  
  handleClick(i) {
    const history = this.history;
    const squares = getBoard(history, i);
    if (calculateWinner(squares) || squares[i]) {
      this.setState({currentStep: history.length});
      return;
    }
    squares[i] = (history.length % 2 === 0) ? 'X' : 'O';
    this.history.push(i);
    this.setState({currentStep: this.history.length});
  }
  
  jumpTo(i) {
    this.setState({currentStep: i});
  }
  
  render() {
    const latestMove = this.history.length - 1;
    const boardAtMove = getBoard(this.history, this.state.currentStep);
    const winner = calculateWinner(getBoard(this.history, latestMove));
    const moves = this.history.map((position, move) => {
      const desc = move ? `Go to move #${move} (${position % 3}, ${Math.floor(position/3)})` : 'Go to game start';
      const text = this.state.currentStep === move ? <b>{desc}</b> : desc;
      return (
        <li key={move}>
          <button onClick={() => this.jumpTo(move)}>
            {text}
          </button>
        </li>
      );
    });
    let status;
    if (winner) {
      status = `Winner: ${winner}`;
    } else {
      if (this.history.length === 9) {
        status = "It's a draw";
      } else {
        status = `Next player: ${((latestMove + 1) % 2 === 0) ? 'X' : 'O'}`;
      }
    }
    
    return (
      <div className="game">
        <div className="game-board">
          <Board 
            squares={boardAtMove}
            onClick={(i) => this.handleClick(i)}
          />
        </div>
        <div className="game-info">
          <div>{status}</div>
          <ol>{moves}</ol>
        </div>
      </div>
    );
  }
}

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

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

scripts

<script src="https://unpkg.com/react/umd/react.development.js"></script>
<script src="https://unpkg.com/react-dom/umd/react-dom.development.js"></script>

style.css

body {
  font: 14px "Century Gothic", Futura, sans-serif;
  margin: 20px;
}

ol, ul {
  padding-left: 30px;
}

.board-row:after {
  clear: both;
  content: "";
  display: table;
}

.status {
  margin-bottom: 10px;
}

.square {
  background: #fff;
  border: 1px solid #999;
  float: left;
  font-size: 24px;
  font-weight: bold;
  line-height: 34px;
  height: 34px;
  margin-right: -1px;
  margin-top: -1px;
  padding: 0;
  text-align: center;
  width: 34px;
}

.square:focus {
  outline: none;
}

.kbd-navigation .square:focus {
  background: #ddd;
}

.game {
  display: flex;
  flex-direction: row;
}

.game-info {
  margin-left: 20px;
}

tic-tac-toe.markdown

Tic Tac Toe

A Pen by Austin Zhu on CodePen.

License.