tutorial-react.js

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>
    );
}

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(const line of lines) {
        const [a, b, c] = line.map((i) => squares[i]);

        if (a === b && b === c && c === a) {
            return a;
        }
    }
    return null;
}

class Board extends React.Component {
    constructor(props) {
        super(props);
        this.state = {
            squares: Array(9).fill(null),
            xIsNext: true,
        };
    }

    handleClick(i) {
        const squares = this.state.squares.slice();
        squares[i] = this.state.xIsNext ? 'X' : 'O';
        this.setState({
            squares: squares,
            xIsNext: !this.state.xIsNext,
        });
    }

    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';
        history.push({ squares });
        this.setState({
            history,
            stepNumber: history.length - 1,
            xIsNext: !this.state.xIsNext,
        });
    }

    jumpTo(step) {
        this.setState({
            history: this.state.history.slice(0, step + 1),
            stepNumber: step,
            xIsNext: (step % 2) === 0,
        })
    }

    render() {
        const history = this.state.history;
        console.log(history);
        console.log(this.state.stepNumber);
        const current = history[this.state.stepNumber];
        const winner = calculateWinner(current.squares);
        const moves = history.map((step, move) => {
            const desc = move === 0 ? `Go to # ${move}` : `Go to game start`;
            return (
                <li key={move}>
                    <button onClick={() => this.jumpTo(move)}>{desc}</button>
                </li>
            )
        });
        const showWinner = `Winner: ${winner}`;
        const nextPlayer = `Next player: ${this.state.xIsNext ? 'X': 'O'}`;
        const status = winner ? showWinner : nextPlayer;
        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>
        );
    }
}

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