Get all cell combinations from a 2d array

generate_combinations.js

/**
 * Recursive mapping
 * @param  array   collection Any 2d array
 * @param  integer index      The starting index (used for recursion)
 * @return array              Array with all possible combination of items
 */
var generate_combinations = function( collection, index ) {
  // Sanity check
  if ( ! collection[ index ] ) {
    // This will never happen unless an invalid index is used
    return [];
  }
  // Get the row for the current recursion
  var row = collection[index];
  // Special handling of the last row
  // Last index means there is no next collection
  if ( collection.length - 1 == index ) {
    // Create a element with the same structure
    var other_rows = [];
    // Divide each cell into seperate rows
    for (var i = 0; i < row.length; i++) {
      var cell = row[i];
      other_rows.push( [ cell ] );
    }
    // Return the last row
    return other_rows;
  }
  // Begin the main recursion logic and start building the result
  var result = [];
  // Recursion! Build the next row before this one.
  // Note that because recursive mapping is called here then it will
  // start at the deepest level and then bubble back to the beginning
  var other_rows = generate_combinations( collection, index + 1 );
  // Loop through this level
  for ( var i = 0; i < row.length; i++ ) {
    // Get the current cell
    var cell = row[i];
    // Uncomment this line to debug the recursion:
    // console.log( 'Depth:' + index + ' @Itteration:' + i +', cell: '+ cell );
    // Loop through the other rows
    for ( var j = 0; j < other_rows.length; j++ ) {
      var other_row = other_rows[j];
      // Create a new record begining with the current cell
      var combination_cell = [ cell ];
      // Combine the new record with all the other combinations
      // from the other rows
      for ( var v = 0; v < other_row.length; v++ ) {
        var other_cell = other_row[v];
        combination_cell.push( other_cell );
      }
      // Finally add the combined cell to the result
      result.push( combination_cell );
    }
  }
  return result;
}

// A test array
var testing = [
  ['B1','B2'],
  ['A1','A2','A3'],
  ['C1','C2'],
];

console.log(
  generate_combinations( testing, 0 )
);