根据https://react.docschina.org/tutorial/tutorial.html学习

import React from 'react';
import ReactDOM from 'react-dom';
import './index.css';

// class Square extends React.Component {
//     render() {
//         function Square(props) {
//             return (
//                 <button className="square" onClick={props.onClick}>
//                     {props.value}
//                 </button>
//             );
//         }
//         return (
//             <button className="square" onClick={() => this.props.onClick()}>
//                 {this.props.value}
//             </button>
//         );
//     }
// }

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 {
    // constructor() {
    //     super();
    //     this.state = {
    //         squares: Array(9).fill(null),
    //         xInNext: true,
    //     }
    // }

    // handleClick(i) {
    //     const squares = this.state.squares.slice();
    //     if(calculateWinner(squares) || squares[i]){
    //         return;
    //     }
    //     squares[i] = this.state.xInNext ? 'X' : 'O';
    //     this.setState({
    //         squares: squares,
    //         xInNext: !this.state.xInNext,
    //     });
    // }

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

    render() {
        // const winner = calculateWinner(this.state.squares);
        // let status;
        // if(winner){
        //     status = 'Winner:'+winner;
        // }else{
        //     status = 'Next player: ' + (this.state.xInNext ? 'X' : 'O');
        // }

        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>
        );
    }
}

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

    handleClick(i) {
        // const history = this.state.history;
        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.xInNext ? 'X' : 'O';
        this.setState({
            history: history.concat([{
                squares: squares,
            }]),
            // squares: squares,
            stepNumber: history.length,
            xInNext: !this.state.xInNext,
        });
    }

    jumpTo(step) {
        this.setState({
            stepNumber: step,
            xInNext: (step % 2) ? false : true,
        })
    }

    render() {
        const history = this.state.history;
        // const current = history[history.length - 1];
        const current = history[this.state.stepNumber];
        const winner = calculateWinner(current.squares);

        const moves = history.map((step, move) => {
            const desc = move ? 'Move #' + move : 'Game start';
            return (
                <li key={move}>
                    <a href="#" onClick={() => this.jumpTo(move)}>{desc}</a>
                </li>
            );
        });

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

function UserGreeting(props) {
    return <h1>Welcome back!</h1>;
}

function GuestGreeting(props) {
    return <h1>Please sign up.</h1>;
}

function Greeting(props) {
    const isLoggedIn = props.isLoggedIn;
    if (isLoggedIn) {
        return <Game />;
    }
    return <GuestGreeting />;
}

ReactDOM.render(
    // <Game />,
    <Greeting isLoggedIn={false} />,
    document.getElementById('root')
);

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

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