Create tic-tac-toe.js in React (#997)

tic_tac_toe/javascript/react/tic-tac-toe.js

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+import React from 'react';
+import ReactDOM from 'react-dom';
+import './index.css';
+
+
+// Initialization of variables.
+let human, computer;
+
+// Dummy components. Only returns JSX to render when called by Board.
+function Square(props) {
+  return (
+    <button className="square" onClick={props.onClick} value={props.number}>
+      {props.value}
+    </button>
+  );
+}
+
+function Button(props) {
+  return (
+    <button className="reset" onClick={props.onClick}>
+      Reset?
+    </button>
+  );
+}
+
+
+// The actual board. Where all of the rendering of the actual game is, with the algorithim.
+
+class Board extends React.Component {
+  constructor(props) {
+    super(props);
+    this.state = {
+      squares: Array(9).fill(null), // Board definition.
+      xIsNext: props.isX, // Recieving from Game based on user input. Returns true or false
+    }
+  }
+
+
+// Calls the square and adds clicking functions to it.
+  renderSquare(i) {
+    return (
+      <Square
+        value={this.state.squares[i]}
+        number={i} // testing purposes
+        onClick={() => this.handleClick(i)}
+      />
+    );
+  }
+
+
+// changes the state everytime a button is clicked, but tests if the game isn't over before
+  handleClick(i) {
+
+    computer = this.state.xIsNext ? 'O' : 'X';
+    human = this.state.xIsNext ? 'X' : 'O';
+
+    const squares = this.state.squares.slice();
+    if (calculateWinner(squares) || squares[i] || isItATie(squares)) {
+      return;
+    }
+    squares[i] = this.state.xIsNext ? 'X' : 'O';
+    this.setState({
+      squares: squares,
+      xIsNext: !this.state.xIsNext,
+    },
+    this.AIDecider
+    );
+  }
+
+
+// resets the board when the button is clicked.
+  resetClick() {
+    this.setState({
+      squares: Array(9).fill(null), // Clears the board.
+      xIsNext: this.props.isX, // if true, returns 'X'. else, returns 'O'.
+    });
+  }
+
+
+// Easier to just define the function and keep calling it with this
+  copyBoard(board) {
+    return board.slice();
+  }
+
+  /*
+  Checks to make sure if the move that AIDecider, minScore, and maxScore is valid.
+  If not, doesn't return anything.
+  If it is valid, it returns every possible combination in arrays.
+  */
+
+  validMove(index, player, board) {
+    let thisCopy = this.copyBoard(board);
+    if (thisCopy[index] === null) {
+      thisCopy[index] = player;
+      return thisCopy;
+    } else {
+      return null;
+    }
+  }
+
+  /*
+  The actual decider, and beginning of the MiniMax algorithim.
+  Calls maxScore, which calls minScore until it finds an index.
+  Then, copies the board and gives back the board with the decision.
+  */
+
+  AIDecider() {
+    let boardCopy = this.copyBoard(this.state.squares);
+    let move = null;
+    let bestMoveScore = -100;
+    let newBoard = null;
+    let publishedBoard = null;
+    // doesn't do anything if the game is over
+    if (calculateWinner(boardCopy) === computer || calculateWinner(boardCopy) === human || isItATie(boardCopy)) {
+      return null;
+    }
+
+    /*
+    The initial loop that suggests any and all moves possible. Calls maxScore which
+    has its own loop which adds a move and calls validMove
+    (therefore putting it a move ahead), and maxScore calls minScore that has its own loop
+    (therefore putting it two moves ahead). Then, decides by point incentive whether
+    it is a good move or not.
+    */
+
+    for (let i = 0; i < boardCopy.length; i++) {
+      newBoard = this.validMove(i, computer, boardCopy);
+      if (newBoard) {
+        let moveScore = this.maxScore(newBoard);
+        if (moveScore > bestMoveScore) {
+          bestMoveScore = moveScore;
+          move = i;
+        }
+      }
+    }
+
+    /*
+    When the loop is over, it will assign the index that is the best move to play.
+    Assigns the new index with whatever the computer is playing (X or O), then adds it onto
+    a copy of the board (publishedBoard) where it will be change the state of the board.
+    setTimeout given for user experience (giving the illusion that the computer is "thinking").
+    */
+
+    publishedBoard = boardCopy;
+    publishedBoard[move] = computer;
+    setTimeout(() => {
+      this.setState({
+        squares: publishedBoard,
+        xIsNext: !this.state.xIsNext
+      });
+    }, 300);
+  }
+
+  /*
+  minScore and maxScore call on each other where they add more possible moves onto
+  the copied board until it is either a tie, or someone has won with the theoretical
+  boards. Then, returns a number value where the loop in AIDecider will start again
+  until the loop runs out.
+  */
+
+  minScore(board) {
+    if (calculateWinner(board) === human) {
+      return -10;
+    } else if (calculateWinner(board) === computer) {
+      return 10;
+    } else if (isItATie(board)) {
+      return 0;
+    } else {
+      let bestMoveValue = -100;
+      let move = 0;
+      for (let i = 0; i < board.length; i++) {
+        let newBoard = this.validMove(i, computer, board);
+        if (newBoard) {
+          let predictedMoveValue = this.maxScore(newBoard);
+          if (predictedMoveValue > bestMoveValue) {
+            bestMoveValue = predictedMoveValue;
+            move = i;
+          }
+        }
+      }
+      return bestMoveValue;
+    }
+  }
+
+  // Called first by AIDecider, then calls minScore
+
+  maxScore(board) {
+    if (calculateWinner(board) === human) {
+      return -10;
+    } else if (calculateWinner(board) === computer) {
+      return 10;
+    } else if (isItATie(board)) {
+      return 0;
+    } else {
+      let bestMoveValue = 100;
+      let move = 0;
+      for (let i = 0; i < board.length; i++) {
+        let newBoard = this.validMove(i, human, board);
+        if (newBoard) {
+          let predictedMoveValue = this.minScore(newBoard);
+          if (predictedMoveValue < bestMoveValue) {
+            bestMoveValue = predictedMoveValue;
+            move = i;
+          }
+        }
+      }
+      return bestMoveValue;
+    }
+  }
+
+  render() {
+    const winner = calculateWinner(this.state.squares);
+    const tie = isItATie(this.state.squares);
+    let status, button = null;
+
+    if (winner) {
+      status = "Winner: " + winner;
+      button = <Button onClick={() => this.resetClick()}/>
+    } else if (tie) {
+      status = "It's a tie!";
+      button = <Button onClick={() => this.resetClick()}/>
+    } else {
+      status = "Your turn, " + (this.state.xIsNext ? 'X' : 'O');
+    }
+
+    return (
+      <div>
+        <div className="status">{status}</div>
+        <div style={{textAlign: 'center'}}>{button}</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>
+    );
+  }
+}
+
+
+// Initialization of game. Passes the choice of the user to Board, where the actual game will render.
+class Game extends React.Component {
+  constructor() {
+    super();
+    this.state = {
+      hasChosen: false,
+      isX: true,
+    }
+  }
+
+  question() {
+    return (
+      <div className='questionRow'>
+        Tic Tac Toe
+        <br />
+        <br />
+        X or O?
+        <br />
+        <button className='button' onClick={() => this.test(true)}>X</button>
+        <button className='button' onClick={() => this.test(false)}>O</button>
+      </div>
+    );
+  }
+
+  test(bool) {
+    if (bool) {
+      this.setState({
+        hasChosen: true,
+        isX: true,
+      });
+    } else {
+      this.setState({
+        hasChosen: true,
+        isX: false,
+      });
+    }
+  }
+
+  render() {
+    let board = null;
+
+    if (!this.state.hasChosen) {
+      board = this.question();
+    } else {
+      board = <Board isX={this.state.isX} />
+    }
+
+    return (
+      <div>
+        <div className="game">
+          <div className="game-board">
+          {board}
+          </div>
+        </div>
+      </div>
+    );
+  }
+}
+
+/*
+Where it calculates if there is a possible winner with the MiniMax loops, or ties.
+Note: status does not render until there is an actual winner (not theoretical winners
+made up by MiniMax), tested by the actual state of the board.
+*/
+
+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;
+}
+
+function isItATie(squares) {
+  let copy = squares.slice();
+  if (copy.some(element => !element)) {
+    return false;
+  } else {
+    return true;
+  }
+}
+
+ReactDOM.render(
+  <Game />,
+  document.getElementById('root')
+);