react入门教程案例井字棋（包含改进代码）

1、index.js

import React from 'react';
import ReactDOM from 'react-dom';
import './index.css'
function Square (props){
    if(props.winBtn){
    /*每当有人获胜时，高亮显示连成一线的 3 颗棋子。*/
        return (
            <button style={{backgroundColor:"MediumSpringGreen"}} className="square" onClick={props.onClick}>
                {props.value}
            </button>
        );
    }else {
        return (
            <button className="square" onClick={props.onClick}>
                {props.value}
            </button>
        );
    }
}

class Board extends React.Component {

    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>*/
                /*使用两个循环来渲染出棋盘的格子，而不是在代码里写死（hardcode）*/
                Array(3).fill(null).map((rowitem,index)=>
                    <div key={'row'+index} className="board-row">
                        {
                            Array(3).fill(null).map((columitem,j) =>
                            {return <Square
                                key = {j}
                                /*索引规律
                                    index  j   棋盘数组索引
                                      0    0      0
                                      0    1      1
                                      0    2      2
                                      1    0      3
                                      1    1      4
                                      1    2      5
                                      2    0      6
                                      2    1      7
                                      2    2      8
                                      3*index+j = 棋盘数组索引*/
                                winBtn = {this.props.winBtn[3*index+j]}
                                value={this.props.squares[3*index+j]}
                                onClick={()=> this.props.onClick(3*index+j)}
                            />}
                            )
                        }
                    </div>
                )}
            </div>
        );
    }
}

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

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

    jumpTo(step) {
        this.setState({
            stepNumber: step,
            xIsNext: (step % 2) === 0,
        });
    }
    /**
     * 根据数据做引获取坐标
     */
    getXYByIndex(index){
        let xy = "";
        switch (index) {
            case 0:xy="1,1";break;
            case 1:xy="2,1";break;
            case 2:xy="3,1";break;
            case 3:xy="1,2";break;
            case 4:xy="2,2";break;
            case 5:xy="3,2";break;
            case 6:xy="1,3";break;
            case 7:xy="2,3";break;
            case 8:xy="3,3";break;
            default:break;
        }
        return xy;
    }

    /**
     * 历史记录排序
     */
    order (){
        const isDesc = this.state.isDesc;
        this.setState({
            isDesc: !isDesc,
        });
    }

    render() {
        const history = this.state.history;
        const current = history[this.state.stepNumber];
        let winMap = calculateWinner(current.squares,this);
        let winner;
        if(winMap == null){
            winner = null;
            winMap = {};
            winMap['winBtn'] = Array(9).fill(null);
        }else {
            winner = winMap.winner;
        }
        const moves = history.map((step, move) => {
            const discrib = move ?
                'Go to move #' + move + '('+this.state.xys[move-1]+')':/*在游戏历史记录列表显示每一步棋的坐标，格式为 (列号, 行号)。*/
                'Go to game start';
            let history_btn = "";
            if(move === this.state.stepNumber){
            	//在历史记录列表中加粗显示当前选择的项目。
                history_btn = <button style={{fontWeight:600}} onClick={() => this.jumpTo(move)}>{discrib}</button>
            }else {
                history_btn = <button onClick={() => this.jumpTo(move)}>{discrib}</button>;
            }
            return (
                <li key={move}>{history_btn}</li>
            );
        });
        let status;//操作提示
        if (winner) {
            status = 'Winner: ' + winner ;
        } else {
            status = 'Next player: ' + (this.state.xIsNext ? 'X' : 'O');
        }
        let buttonName;//历史记录顺序按钮名称
        let finalMoves;//历史记录数据
        if(this.state.isDesc){
            buttonName = '升序';
            finalMoves = moves;
        }else {
            buttonName = '降序';
            finalMoves = moves.reverse();
        }
        return (
            <div className="game">
                <div className="game-board">
                    <Board
                        winBtn={winMap == null ? null : winMap.winBtn}
                        squares={current.squares}
                        onClick={(i) => this.handleClick(i)}
                    />
                </div>
                <div className="game-info">
                    <div>{status}&nbsp;&nbsp;&nbsp;&nbsp;
					/*添加一个可以升序或降序显示历史记录的按钮。*/
					<button onClick={() =>this.order()}>{buttonName}</button></div>
                    <ol>{finalMoves}</ol>
                </div>
            </div>
        );
    }
}

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

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

function calculateWinner(squares,obj) {
    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]) {
            let winBtn = Array(9).fill(null);
            if(winBtn.indexOf(true) < 0){
                winBtn[a] = true;
                winBtn[b] = true;
                winBtn[c] = true;
            }
            const result = {"winner":squares[a],"winBtn":winBtn};
            return result;
        }else {
        /*当无人获胜时，显示一个平局的消息。*/
            let endFlag = true;
            for(let j in squares){
                if(squares[j] == null){
                    endFlag = false;
                }
            }
            if(endFlag){
                const result = {"winner":'平局',"winBtn":Array(9).fill(null)};
                return result;
            }
        }
    }
    return null;
}

2、index.css

body {
  font: 14px "Century Gothic", Futura, sans-serif;
  margin: 20px;
}

ol, ul {
  padding-left: 30px;
}

.board-row:after {
  clear: both;
  content: "";
  display: table;
}

.status {
  margin-bottom: 10px;
}

.square {
  background: #fff;
  border: 1px solid #999;
  float: left;
  font-size: 24px;
  font-weight: bold;
  line-height: 34px;
  height: 34px;
  margin-right: -1px;
  margin-top: -1px;
  padding: 0;
  text-align: center;
  width: 34px;
}

.square:focus {
  outline: none;
}

.kbd-navigation .square:focus {
  background: #ddd;
}

.game {
  display: flex;
  flex-direction: row;
}

.game-info {
  margin-left: 20px;
}

3、index.html

<div id="errors" style="
  background: #c00;
  color: #fff;
  display: none;
  margin: -20px -20px 20px;
  padding: 20px;
  white-space: pre-wrap;
"></div>
<div id="root"></div>
<script>
  window.addEventListener('mousedown', function(e) {
    document.body.classList.add('mouse-navigation');
    document.body.classList.remove('kbd-navigation');
  });
  window.addEventListener('keydown', function(e) {
    if (e.keyCode === 9) {
      document.body.classList.add('kbd-navigation');
      document.body.classList.remove('mouse-navigation');
    }
  });
  window.addEventListener('click', function(e) {
    if (e.target.tagName === 'A' && e.target.getAttribute('href') === '#') {
      e.preventDefault();
    }
  });
  window.onerror = function(message, source, line, col, error) {
    var text = error ? error.stack || error : message + ' (at ' + source + ':' + line + ':' + col + ')';
    errors.textContent += text + '\n';
    errors.style.display = '';
  };
  console.error = (function(old) {
    return function error() {
      errors.textContent += Array.prototype.slice.call(arguments).join(' ') + '\n';
      errors.style.display = '';
      old.apply(this, arguments);
    }
  })(console.error);
</script>

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