docusaurus/v2/website/components/Tictactoe/index.js

import React from 'react';
import Helmet from 'react-helmet';
import Layout from '@theme/Layout';
import Board from './board';
import styles from './styles.css';

class Game extends React.Component {
  constructor(props) {
    super(props);
    this.state = {
      history: [
        {
          squares: Array(9).fill(null)
        }
      ],
      stepNumber: 0,
      xIsNext: true
    };
  }

  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;
  }

  handleClick(i) {
    const history = this.state.history.slice(0, this.state.stepNumber + 1);
    const current = history[history.length - 1];
    const squares = current.squares.slice();
    if (this.calculateWinner(squares) || squares[i]) {
      return;
    }
    squares[i] = this.state.xIsNext ? 'X' : 'O';
    this.setState({
      history: history.concat([
        {
          squares: squares
        }
      ]),
      stepNumber: history.length,
      xIsNext: !this.state.xIsNext
    });
  }

  jumpTo(step) {
    this.setState({
      stepNumber: step,
      xIsNext: step % 2 === 0
    });
  }

  render() {
    const history = this.state.history;
    const current = history[this.state.stepNumber];
    const winner = this.calculateWinner(current.squares);

    const moves = history.map((step, move) => {
      const desc = move ? 'Go to move #' + move : 'Go to game start';
      return (
        <li key={move}>
          <button onClick={() => this.jumpTo(move)}>{desc}</button>
        </li>
      );
    });

    let status;
    if (winner) {
      status = 'Winner: ' + winner;
    } else {
      status = 'Next player: ' + (this.state.xIsNext ? 'X' : 'O');
    }

    return (
      <div className={styles.game}>
        <div className={styles.gameBoard}>
          <Board squares={current.squares} onClick={i => this.handleClick(i)} />
        </div>
        <div className={styles.gameInfo}>
          <div>{status}</div>
          <ol>{moves}</ol>
        </div>
      </div>
    );
  }
}

export default Game;