Thumbtack Connect 4

thumbtackConnect4.js

/*
 * Earning Thumbtack swag in JS
 * http://www.thumbtack.com/engineering/how-we-got-people-to-earn-our-schwag/
 */

// The board
// hard-coded here, but could be easily loaded in via AJAX
var thumbtackBoard = [
  [".", ".", ".", ".", ".", ".", "."],
  [".", ".", ".", ".", ".", ".", "."],
  [".", ".", "O", ".", ".", ".", "."],
  [".", ".", "X", "O", "X", "X", "."],
  [".", ".", "X", "X", "O", "O", "X"],
  [".", ".", "O", "X", "X", "O", "X"]
];

var Connect4 = function (board, pieces, length) {
	this.board = board;
	this.pieces = pieces || ['O', 'X'];
	this.connectLength = length || 4;
	this.currentRow = 0;
	this.currentColumn = 0;
}

Connect4.prototype.search_rows = function (piece, direction) {
	var down = 1;
	if (direction === 'diagonal-left') step = -1;
	else if (direction === 'diagonal-right') step = 1;
	else if (direction === 'straight-down') step = 0;
	else if (direction === 'straight-right') step = 1, down = 0;
	for (var i = 1; i < this.connectLength; i++) {
		try {
			if (this.board[this.currentRow+(down*i)][this.currentColumn+(step*i)] === piece) {
				if (i === (this.connectLength-1)) return true;
				else continue;
			} 
			else break;
		} catch (err) {
			break;
		}
	}
	return false;
}

Connect4.prototype.find_winner = function () {
	for (this.currentRow = 0; this.currentRow < this.board.length; this.currentRow++) {
		for (this.currentColumn = 0; this.currentColumn < this.board[this.currentRow].length; this.currentColumn++) {
			var pieceIndex = this.pieces.indexOf(this.board[this.currentRow][this.currentColumn]);
			if (pieceIndex !== -1) {
				var piece = this.pieces[pieceIndex];
				if (this.currentRow < this.board.length - (this.connectLength-1)) {
					if (this.search_rows(piece, 'diagonal-left')) return piece;
					if (this.search_rows(piece, 'diagonal-right')) return piece;
					if (this.search_rows(piece, 'straight-down')) return piece;
				}
				if (this.search_rows(piece, 'straight-right')) return piece;
			}
		}
	}
}

var winner = (new Connect4(thumbtackBoard)).find_winner();
if (winner) alert('Winner is ' + winner);
else alert('No winner');