Dyck Path

Consider a n x n grid with indexes of top left corner as (0, 0). Dyck path is a staircase walk from bottom left, i.e., (n-1, 0) to top right, i.e., (0, n-1) that lies above the diagonal cells (or cells on line from bottom left to top right). The task is to count the number of Dyck Paths from (n-1, 0) to (0, n-1)

function dyckPath(n)
{
  var res = 1;
  for(var i = 0; i < n; ++i)
  {
    res *= (2 * n - i);
    res /= (i + 1);
  }
  return res / (n+1);
}