TicTacToe game of any size that determines a winner in O(1)

tictactoeconstanttime.js

class TicTacToe {
  constructor(size) {
    this.size = size
    this.center = Math.floor(this.size / 2)

    this.state = {
      board: [],
      score: [],
      move: 0,
    }
  }

  initGame() {
    const board = []

    for (let i = 0; i < this.size; i++) {
      board.push(Array(this.size).fill(0))
    }

    this.state.board = board
    this.state.score = Array(2 + (2 * this.size)).fill(0)
  }

  onMove(row, column, player) {
    const { board } = this.state

    if (board[row][column] !== 0) return console.log('Move already taken. Please choose another.')

    this.updateBoard(row, column, player)
    this.updateScore(row, column, player)

    this.printBoard()
  }

  updateBoard(row, column, player) {
    const { board } = this.state

    switch (player) {
      case 1: 
        board[row][column] = 1
        this.state.move = this.state.move + 1
        break
      case -1:
        board[row][column] = -1
        this.state.move = this.state.move + 1
        break
      default:
        return null
    }
  }

  updateScore(row, column, player) {
    const { score } = this.state
    const leftDiagonalIndex = this.size * 2
    const rightDiagonalIndex = this.size * 2 + 1

    if (row === this.center && column === this.center) {
      score[leftDiagonalIndex] += player
      this.checkScore(leftDiagonalIndex, player)

      score[rightDiagonalIndex] += player
      this.checkScore(rightDiagonalIndex, player)
    } else {
      if (row === column) {
        score[leftDiagonalIndex] += player
        this.checkScore(leftDiagonalIndex, player)
      }
      
      if (row + column === this.size - 1) {
        score[rightDiagonalIndex] += player
        this.checkScore(rightDiagonalIndex, player)
      }
    }

    score[row] += player
    this.checkScore(row, player)

    score[column + this.size] += player
    this.checkScore(column + this.size, player)

    if (this.move === Math.pow(this.size, 2)) return this.printStalemate()

    this.printScore()
  }

  checkScore(index, player) {
    const { score } = this.state

    if (score[index] === this.size || score[index] === -Math.abs(this.size)) {
      return this.printWinner(player)
    }
  }

  printBoard() {
    console.log(this.state.board)
  }

  printScore() {
    console.log(this.state.score)
  }

  printWinner(player) {
    console.log(`*!*@*# ${player} IS THE WINNER #*@*!*`)
  }

  printStalemate() {
    console.log('STALEMATE')
  }
}

const game = new TicTacToe(4)
game.initGame()
game.onMove(0,0,1)
game.onMove(1,1,-1)
game.onMove(1,0,1)
game.onMove(0,2,-1)
game.onMove(2,2,1)
game.onMove(2,1,-1)
game.onMove(1,2,1)
game.onMove(2,0,-1)
game.onMove(3,3,1)
game.onMove(0,1,-1)
game.onMove(2,3,1)
game.onMove(3,1,-1)