def log(base, n):
    high = n
    low = 0
    guess = n / 2
    epsilon = 0.005
    cnt = 0
    while cnt <= 100:
        r = base**guess
        if abs(r - n) < epsilon:
            return guess
        if r > n:
            high = guess
        if r < n:
            low = guess
        cnt += 1
        guess = (low + high) / 2
    return guess

for i in range(2, 17):
    print(i, "=", log(2, i))

>>> 2 = 1.0
3 = 1.5849609375
4 = 2.0
5 = 2.32177734375
6 = 2.583984375
7 = 2.807861328125
8 = 3.0
9 = 3.170654296875
10 = 3.321533203125
11 = 3.458984375
12 = 3.58447265625
13 = 3.70068359375
14 = 3.8076171875
15 = 3.90655517578125
16 = 4.0

#define X_SZE 4
#define Y_SZE 5

const int matrix[Y_SZE][X_SZE] = {1,  2,  3,  4,
				  5,  6,  7,  8,
				  9,  10, 11, 12,
				  13, 14, 15, 16,
				  17, 18, 19, 20};

void spiral(void)
{
  int i, dir, x_min, y_min = 0;
  int x_max = X_SZE-1;
  int y_max = Y_SZE-1;

  while((x_min <= x_max) && (y_min <= y_max))
    {
      switch(dir%4)
	{
	case 0:
	  for(i=x_min;i<=x_max;i++)
	    printf("%d ", matrix[y_min][i]);
	  y_min++;
	  break;
	case 1:
	  for(i=y_min;i<=y_max;i++)
	    printf("%d ", matrix[i][x_max]);
	  x_max--;
	  break;
	case 2:
	  for(i=x_max;i>=x_min;i--)
	    printf("%d ", matrix[y_max][i]);
	  y_max--;
	  break;
	case 3:
	  for(i=y_max;i>=y_min;i--)
	    printf("%d ", matrix[i][x_min]);
	  x_min++;
	  break;
	default:
	  printf("Error!");
	  break;
	}
      dir++;
    }
}

def spiral(A):
    _spiral(A,"")

def _spiral(A,string):
    for j in range(len(A[0])):
        string += str(A[0][j]) + ' '

    for i in range(1,len(A)):
        string += str(A[i][len(A[0]) - 1]) + ' '

    for j in reversed(range(len(A[0]) - 1)):
        string += str(A[len(A) - 1][j]) + ' '

    for i in reversed(range(1,len(A) - 1)):
        string += str(A[i][0]) + ' '

    if (len(A) > 2) and (len(A[0]) > 2):
        _spiral([x[1:len(A[0]) - 1] for x in A[1:len(A) - 1]],string)
    else:
        print(string)

let matrix = [
[1,  2,  3,  4],
[5,  6,  7,  8],
[9, 10, 11, 12],
[13, 14, 15, 16],
[17, 18, 19, 20]];

const output = [];
while (matrix.length) {
  matrix[0].map(val => { output.push(val); }); 
  matrix.shift();
  if (matrix.length) matrix = rotateCounterClockwise(matrix);
}

console.log(output);

function rotateCounterClockwise(array) {
  const rightColIndex = array[0].length-1;
  return array[0].map((col, i) => { 
    return array.map(row => { return row[rightColIndex-i]; });
  });
}