react_pj/src/index.js

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

// rename to index, then run npm start.
/* ========================================================================== */
/*                                   Square                                   */
/* ========================================================================== */

// class Square2 extends React.Component {
//   constructor(props) {
//     // init a state.
//     super(props);
//     this.state = {
//       value: null,
//     };
//   }
//   render() {
//     return (
//       <button
//         className="square"
//         onClick={
//           () => this.props.onClick()
//         }
//       >
//         {this.props.value}
//       </button>
//     );
//   }
// }

// less code, less effort.
function Square(props) {
  return (
    <button className="square" onClick={props.onClick}>
      {props.value}
    </button>
  );
}

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

  handleClick(i) {
    // to update what to display in the little squres in The board.
    const squares = this.state.squares.slice(); // make a copy of squares array.
    if (calculateWinner(squares) || squares[i]) {
      return;
    }
    squares[i] = this.state.xIsNext ? "X" : "O"; // if true then x. else o
    this.setState({
      squares: squares,
      xIsNext: !this.state.xIsNext, // flip~ now.
    });
  }

  handleClick2() {
    // to update what to display in the little squres in The board.
    const squares = this.state.squares.slice(); // make a copy of squares array.
    this.setState({
      squares: Array(9).fill(null),
    });
  }

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

  resetbutton() {
    return <button className="button" onClick={()=>this.handleClick2()}>{"reset button~"}</button>;
  }

  render() {
    const winner = calculateWinner(this.state.squares);
    let status;
    if (winner) {
      status = "winner is: " + winner;
    } else {
      status = "Next player: " + (this.state.xIsNext ? "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 className="buton">{this.resetbutton()}</div> 
      </div>
    );
  }
}


/* ========================================================================== */
/*                               cal winner who                               */
/* ========================================================================== */
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;
}
/* ========================================================================== */
/*                                    game                                    */
/* ========================================================================== */
class Game extends React.Component {
  render() {
    return (
      <div className="game">
        <div className="game-board">
          <Board />
        </div>
        <div className="game-info">
          <div>{/* status */}</div>
          <ol>{/* TODO */}</ol>
        </div>
      </div>
    );
  }
}

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


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