sudoku.js

const board = [
    [7,	2,	6,	4,	9,	3,	8,	1,	5],
    [3,	1,	5,	7,	2,	8,	9,	4,	6],
    [4,	8,	9,	6,	5,	1,	2,	3,	7],
    [8,	5,	2,	1,	4,	7,	6,	9,	3],
    [6,	7,	3,	9,	8,	5,	1,	2,	4],
    [9,	4,	1,	3,	6,	2,	7,	5,	8],
    [1,	9,	4,	8,	3,	6,	5,	7,	2],
    [5,	6,	7,	2,	1,	4,	3,	8,	9],
    [2,	3,	8,	5,	7,	9,	4,	6,	1],
]

/**
 * Checks if the list of values is a valud sudoku combination of numbers.
 *
 * Constraints:
 *   - 9 values total
 *   - Must be integers 1 - 9
 *   - No duplicate values
 * 
 * @param  {[type]}  values [description]
 * @return {Boolean}        [description]
 */
var isValid = function(values) {
	var seen = [];

	// Not 9 values.
	if(values.length != 9) {
		return false;
	}

	// Check for duplicates
	for(var i = 0; i < values.length; i++) {
		if(seen.indexOf(values[i]) !== -1) {
			return false;
		}

		seen.push(values[i]);
	}

	// Only values 1-9
	return (seen.length === 9);
}

/**
 * Inspects the board to verify all rows, columns, and 3x3 tiles are valid.
 * 
 * @param  {[type]} rows [description]
 * @return {[type]}      [description]
 */
var checkBoard = function(board) {
	var cols = [[], [], [], [], [], [], [], [], []];
	var tiles = [[], [], [], [], [], [], [], [], []];

	// Check rows
	for(var i = 0; i < board.length; i++) {
		if(!isValid(board[i])) {
			return false;
		}

		for(var j = 0; j < board[i].length; j++) {
			// Build column list
			cols[j].push(board[i][j]);

			// Build tile list
			if(i <= 3) {
				if(j <= 3) {
					tiles[0].push(board[i][j]);
				}
				else if(j <= 6) {
					tiles[1].push(board[i][j]);
				}
				else if(j <= 9) {
					tiles[2].push(board[i][j]);
				}
			}
			else if(i <= 6) {
				if(j <= 3) {
					tiles[3].push(board[i][j]);
				}
				else if(j <= 6) {
					tiles[4].push(board[i][j]);
				}
				else if(j <= 9) {
					tiles[5].push(board[i][j]);
				}
			}
			else if(i <= 9) {
				if(j <= 3) {
					tiles[6].push(board[i][j]);
				}
				else if(j <= 6) {
					tiles[7].push(board[i][j]);
				}
				else if(j <= 9) {
					tiles[8].push(board[i][j]);
				}
			}
		}
	}

	// Check columns
	for(var i = 0; i < cols.length; i++) {
		if(!isValid(cols[i])) {
			return false;
		}
	}

	console.log(tiles);

	// Check tiles
	for(var i = 0; i < tiles.length; i++) {
		if(!isValid(tiles[i])) {
			return false;
		}
	}

	return true;
}


if(checkBoard(board)) {
	console.log('Board is VALID!');
}
else {
	console.log('Board is INVALID!');
}