tictactoe.js

class TTTGame {
  constructor() {
    this.board = [[null,null,null],[null,null,null],[null,null,null]]
    this.currentTurn = 'x'
    this.gameState = true
  }

  reset() {
    this.board = [[null,null,null],[null,null,null],[null,null,null]]
    this.currentTurn = 'x'
    this.gameState = true
  }

  checkForWin() {
    const verticalWin = this.checkForVerticalWin()
    const horizontalWin = this.checkForHorizontalWin()
    const firstDiagonalWin = this.checkForFirstDiagonalWin()
    const secondDiagonalWin = this.checkForSecondDiagonalWin()
    if (verticalWin) return verticalWin
    if (horizontalWin) return horizontalWin
    if (firstDiagonalWin) return firstDiagonalWin
    if (secondDiagonalWin) return secondDiagonalWin
    return false
  }

  checkForMatches(val1, val2, val3) {
    if (val1 === val2 && val1 === val3) {
      this.gameState = false
      return {result: true, winner: val1}
    }
    return false
  }

  checkForHorizontalWin() {
    for (let row = 0; row < 3; row++) {
      const firstValue = this.board[row][0]
      const secondValue = this.board[row][1]
      const thirdValue = this.board[row][2]
      if (!firstValue) {
        continue
      }
      const result = this.checkForMatches(firstValue, secondValue, thirdValue)
      if (result) {
        return result
      }
    }
    return false
  }

  checkForVerticalWin() {
    for (let col = 0; col < 3; col++) {
      const firstValue = this.board[0][col]
      const secondValue = this.board[1][col]
      const thirdValue = this.board[2][col]
      if (!firstValue) {
        continue
      }
      const result = this.checkForMatches(firstValue, secondValue, thirdValue)
      if (result) {
        return result
      }
    }
    return false
  }

  checkForFirstDiagonalWin() {
    const firstValue = this.board[0][0]
    const secondValue = this.board[1][1]
    const thirdValue = this.board[2][2]
    if (!firstValue) {
      return false
    }
    return this.checkForMatches(firstValue, secondValue, thirdValue)
  }

  checkForSecondDiagonalWin() {
    const firstValue = this.board[0][2]
    const secondValue = this.board[1][1]
    const thirdValue = this.board[2][0]
    if (!firstValue) {
      return false
    }
    return this.checkForMatches(firstValue, secondValue, thirdValue)
  }

  placeX({row, col} = {}) {
    this.#play(row, col, 'x')
    const check = this.checkForWin()
    if (check) {
      console.log(`${check.winner} wins`)
    }
  }

  placeO({row, col} = {}) {
    this.#play(row, col, 'o')
    const check = this.checkForWin()
    if (check) {
      console.log(`${check.winner} wins`)
    }
  }

  #play(row, col, char) {
    if (!this.gameState) {
      throw new Error("game over")
    }
    if (typeof row !== 'number' || typeof col !== 'number') {
      throw new Error("that's not a valid space")
    }
    if (this.currentTurn != char) {
      throw new Error("not your turn, player")
    }
    if (row < 0 || col < 0 || row > 2 || col > 2 ) {
      throw new Error("that's not a valid space")
    }
    if (this.board[row][col]) {
      throw new Error('that space is already taken')
    }
    this.board[row][col] = char
    if (char === 'x') {
      this.currentTurn = 'o'
    }
    if (char === 'o') {
      this.currentTurn = 'x'
    }
    return this
  }
}