index.js

import PropTypes from 'prop-types'
import React from 'react'
import ReactDOM from 'react-dom'
import './index.css'

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

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

  render() {
    return (
      <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>
    )
  }
}

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

  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 (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 = calculateWinner(current  .squares)

    const moves = history.map(((step, move) => {
      const desc = move ? `Go to mvoe # ${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="game">
        <div className="game-board">
          <Board
            squares={current.squares}
            onClick={(i) => this.handleClick(i)}
          />
        </div>
        <div className="game-info">
          <div>{status}</div>
          <ol>{moves}</ol>
        </div>
      </div>
    )
  }
}

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

Square.propTypes = {
  value: PropTypes.string,
  onClick: PropTypes.func,
}

Board.propTypes = {
  squares: PropTypes.array,
  onClick: PropTypes.func,
}

ReactDOM.render(
  <Game />,
  document.getElementById('root')
)

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]
    // Check three of the marks form a straight line in the given position
    if (squares[a] && squares[a] === squares[b] && squares[a] === squares[c]) {
      return squares[a]
    }
  }
  return null
}