JSX语法（二）+井字棋游戏练习（Day：3）

[XJQ124]

任务：完成井字棋练习和开始React生命周期的学习

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进度：完成了井字棋游戏的练习

1、在 JSX 的大括号内调用 JavaScript 函数

咋天只把引号传递字符串的内容总结了，今天继续总结一下后面的内容： JSX中可以使用大括号的方式来调用函数

const today = new Date();

function formatDate(date) {
  return new Intl.DateTimeFormat(
    'zh-CN',
    { weekday: 'long' }
  ).format(date);
}

export default function TodoList() {
  return (
    <h1>To Do List for {formatDate(today)}</h1>
  );
}

这里通过一个例子来为我们进行了说明。

2、在 JSX 的大括号内使用 JavaScript 对象

const person = {
  name: 'Gregorio Y. Zara',
  theme: {
    backgroundColor: 'black',
    color: 'pink'
  }
};

export default function TodoList() {
  return (
    <div style={person.theme}>
      <h1>{person.name}'s Todos</h1>
      <img
        className="avatar"
        src="https://i.imgur.com/7vQD0fPs.jpg"
        alt="Gregorio Y. Zara"
      />
      <ul>
        <li>Improve the videophone</li>
        <li>Prepare aeronautics lectures</li>
        <li>Work on the alcohol-fuelled engine</li>
      </ul>
    </div>
  );
}

因为我没有在 JSX 的内联 CSS 样式中就已经见过这种写法，呃呃，老实说，CSS都没学过，但是看文档还是有些明悟。

简单来说，就是你要用一个对象的时候，需要用{}大括号将其包起来。

3、井字棋游戏内容：

这是第一次可以实现功能的样子，当然，这个里面还有很多细节我不能很好的理解

import { useState } from 'react';

function Square({ value, onSquareClick}){
  return (
  <button className="square" onClick={onSquareClick}>
    {value}
    </button>
  );
}

export default function Borad(){
  const [xIsNext, setXIsNext] = useState(true);
  const [squares, setSquares] = useState(Array(9).fill(null));

  function handleClick(i){
    if(calculateWinner(squares) || squares[i] ){
      return;
    }
    const nextSquares = squares.slice();
    if(xIsNext){
      nextSquares[i] = "X";
    }else{
      nextSquares[i] = "0"
    }
    setSquares(nextSquares);
    setXIsNext(!xIsNext);
  }
  const winner = calculateWinner(squares);
  let status;
  if (winner) {
    status = "winner: " + winner;
  } else {
    status = "Next Player" + (xIsNext ? "X" : "0");
  }
  return (
    <>
    <div className="status">{status}</div>
    <div className="borad-row">
        <Square value={squares[0]} onSquareClick={() => handleClick(0)} />
        <Square value={squares[1]} onSquareClick={() => handleClick(1)} />
        <Square value={squares[2]} onSquareClick={() => handleClick(2)} />

      </div>
    <div className="borad-row">
        <Square value={squares[3]} onSquareClick={() => handleClick(3)} />
        <Square value={squares[4]} onSquareClick={() => handleClick(4)} />
        <Square value={squares[5]} onSquareClick={() => handleClick(5)} />
      </div>
      <div className="borad-row">
        <Square value={squares[6]} onSquareClick={() => handleClick(6)} />
        <Square value={squares[7]} onSquareClick={() => handleClick(7)} />
        <Square value={squares[8]} onSquareClick={() => handleClick(8)} />
     </div>
    </>  
  );
  }

  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;
  }

截图： 到了这里就是你怎么点都点不动了

下面是最后的版本，可以储存每一步的历史：

import { useState } from 'react';

function Square({ value, onSquareClick }) {
  return (
    <button className="square" onClick={onSquareClick}>
      {value}
    </button>
  );
}

function Board({ xIsNext, squares, onPlay }) {
  function handleClick(i) {
    if (calculateWinner(squares) || squares[i]) {
      return;
    }
    const nextSquares = squares.slice();
    if (xIsNext) {
      nextSquares[i] = 'X';
    } else {
      nextSquares[i] = 'O';
    }
    onPlay(nextSquares);
  }

  const winner = calculateWinner(squares);
  let status;
  if (winner) {
    status = 'Winner: ' + winner;
  } else {
    status = 'Next player: ' + (xIsNext ? 'X' : 'O');
  }

  return (
    <>
      <div className="status">{status}</div>
      <div className="board-row">
        <Square value={squares[0]} onSquareClick={() => handleClick(0)} />
        <Square value={squares[1]} onSquareClick={() => handleClick(1)} />
        <Square value={squares[2]} onSquareClick={() => handleClick(2)} />
      </div>
      <div className="board-row">
        <Square value={squares[3]} onSquareClick={() => handleClick(3)} />
        <Square value={squares[4]} onSquareClick={() => handleClick(4)} />
        <Square value={squares[5]} onSquareClick={() => handleClick(5)} />
      </div>
      <div className="board-row">
        <Square value={squares[6]} onSquareClick={() => handleClick(6)} />
        <Square value={squares[7]} onSquareClick={() => handleClick(7)} />
        <Square value={squares[8]} onSquareClick={() => handleClick(8)} />
      </div>
    </>
  );
}

export default function Game() {
  const [history, setHistory] = useState([Array(9).fill(null)]);
  const [currentMove, setCurrentMove] = useState(0);
  const xIsNext = currentMove % 2 === 0;
  const currentSquares = history[currentMove];

  function handlePlay(nextSquares) {
    const nextHistory = [...history.slice(0, currentMove + 1), nextSquares];
    setHistory(nextHistory);
    setCurrentMove(nextHistory.length - 1);
  }

  function jumpTo(nextMove) {
    setCurrentMove(nextMove);
  }

  const moves = history.map((squares, move) => {
    let description;
    if (move > 0) {
      description = 'Go to move #' + move;
    } else {
      description = 'Go to game start';
    }
    return (
      <li key={move}>
        <button onClick={() => jumpTo(move)}>{description}</button>
      </li>
    );
  });

  return (
    <div className="game">
      <div className="game-board">
        <Board xIsNext={xIsNext} squares={currentSquares} onPlay={handlePlay} />
      </div>
      <div className="game-info">
        <ol>{moves}</ol>
      </div>
    </div>
  );
}

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;
}

截图：

不过这个很多内容我都是照着打了一遍的，还是不是很理解的。

明天的任务会去学习React的生命周期