The challenge: Spiral Matrix Given an m x n matrix, return all elements of the matrix in spiral order.
Example
Input: matrix = [ [1,2,3], [4,5,6], [7,8,9] ]
Output: [1,2,3,6,9,8,7,4,5]
Constraints
m == matrix.length
n == matrix[i].length
1 <= m, n <= 10
-100 <= matrix[i][j] <= 100