minesweeper-shuffle.js

// sets up Board class for an n x n board, where n is the dimension
var Board = function(dimension, mines) {
  this.board = [];
   
  // place all mined cells into array first, followed by mine-less cells
  this.plantMines(dimension,mines);
  
  // perform an in-place shuffle to randomly place mines on board; see algorithm below
  this.board = shuffle(this.board);
  
  // convert 1D array to 2D array
  this.transform(dimension);
  
  console.log('Generated a board of dimensions ' + dimension + ' by ' + dimension); 
  console.log('There are ' + this.countMines() + ' mines on your board!');
};

Board.prototype.plantMines = function(dimension,mines) {
  var initialMinesPlanted = 0,
      numberOfCells = dimension * dimension,
      i;
  for(i = 0; i < numberOfCells; i++) {
    if(initialMinesPlanted < mines) {
      this.board.push(new Cell(true));
      initialMinesPlanted++;
    } else {
      this.board.push(new Cell(false));
    }
  }
}

Board.prototype.transform = function(dimension) {
  var row = [];
  while(this.board.length > dimension) {
    row = this.board.splice(0,dimension);
    this.board.push(row);
    row = [];
  }
};

// retrieves board 2D array
Board.prototype.getBoard = function() {
    return this.board;
};

// checks the number of mines on your board instance
Board.prototype.countMines = function() {
  var count, i, j, row, cell;
  
  count = 0;
  for(i = 0; i < this.board.length; i++) {
    row = this.board[i];
    for(j = 0; j < row.length; j++) {
      cell = row[j];
      if(cell.hasMine){
        count++;
      }
    }
  }
  
  return count;
};

// sets up Cell class, with only hasMine property
var Cell = function(val) {
    this.hasMine = val;
};


Cell.prototype.setMine = function(val) {
  if(typeof val === 'boolean') {
    this.hasMine = val;  
  } else {
    throw new Error('Expected a boolean input but received a ' + typeof val + ' input instead.' ) 
  }
};

// for checking whether the cell has a mine 
Cell.prototype.getMineValue = function() {
  return this.hasMine;
};

/*
Helper Functions
*/
// in-place array shuffle with O(n) time complexity
var shuffle = function(arr) {
  var k, l, temp;
  
  k = arr.length;
  while (k) {
    l = Math.floor(Math.random() * k--);
    temp = arr[k];
    arr[k] = arr[l];
    arr[l] = temp;
  }
  return arr;
};

// sets the dimension and number of mines to be placed on the board
var dimension = 10; 
var mines = 10;
// instantiates a board
var board = new Board(dimension,mines);
console.log(board.getBoard());