reactjs官方demo

import React from "react";
import ReactDom from "react-dom";
import "./index.css";

// class Square extends React.Component {
//     render() {
//         return (
//             <button className="square"
//                     onClick={() => this.props.onClick()}>
//                 {this.props.value}
//             </button>
//         );
//     }
// }
// 在 React 中，有一个命名规范，通常会将代表事件的监听 prop 命名为 on[Event]，将处理事件的监听方法命名为 handle[Event] 这样的格式。
function Square(props) {
    //如果组件只有render方法，并且不包含state，那么我们可以使用函数组件
    //我们把两个 this.props 都替换成了 props。
    return (
        <button className="square" onClick={props.onClick}>
            {props.value}
        </button>
    )

}

class Board extends React.Component {
    //构造函数初始化state，定义了它之后后面的props就可以改为state了。提升到game组件记录history
    // constructor(props) {
    //     super(props);
    //     this.state = {
    //         squares: Array(9).fill(null),
    //         xIsNext: true,
    //     };
    // }


    //定义renderSquare方法传入参数i
    renderSquare(i) {
        // 传递一个名为 value 的 prop 到 Square 当中
        return <Square value={this.props.squares[i]}
                       onClick={() => this.props.onClick(i)}
        />;
    }

    render() {
        //下一次轮到谁
        // const status = "Next Player:" + (this.state.xIsNext ? 'X' : '0');
        return (
            <div>
                {/*由于 Game 组件渲染了游戏的状态，因此我们可以将 Board 组件 render 方法中对应的代码移除。*/}
                {/*<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(props) {
        super(props);
        this.state = {
            history: [
                {
                    squares: Array(9).fill(null),
                }],
            stepNumber: 0,
            xIsNext: true,
        };
    }

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

    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,
        });
    }

    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 move #" + move :
                'Got 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' : '0');
        }

        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>
        );
    }
}

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