pascal.js

const side = 1;

/**
 * Returns the next row based on the row that is passed in.
 */
function row(input = []) {
  console.log(input);

  function recur([first, second, ...rest], next = []) {
    if (!second) {
      return next;
    }

    return recur([second, ...rest], [...next, first + second]);
  }

  return [side, ...recur(input), side];
}

const result = repeat(row, 8, [side]);

/**
 * Utility for repeating a function n times. The output of the first function
 * is the input of the second and so on.
 *
 * Returns an array containing the return values of the function calls
 */
function repeat(fn, times, initial) {
  function recur(value, index = 0, result = []) {
    if (index >= times) {
      return result;
    }

    value = fn(value, index, result);

    result.push(value);

    return recur(value, index + 1, result);
  }

  return recur(initial);
}