Matrix Spiral in JavaScript

matrix_spiral.js

//specs
matrix(2)
[[1,2],
[4,3]]

matrix(4)
[[1,2,3,4],
[12,13,14,5],
[11,16,15,6],
[10,9,8,7]]

function matrix(n) {
  const result = [];

  for (let i = 0; i < n; i++) {
    result.push([]);
  }

  let counter = 1;
  let startColumn = 0;
  let endColumn = n - 1;
  let startRow = 0;
  let endRow = n - 1;

  while (startColumn <= endColumn && startRow <= endRow) {
    for (let i = startColumn; i <= endColumn; i++) {
      result[startRow][i] = counter;
      counter++;
    }
    startRow++;

    for (let i = startRow; i <= endRow; i++) {
      result[i][endColumn] = counter;
      counter++;
    }
    endColumn--;

    for (let i = endColumn; i >= startColumn; i--) {
      result[endRow][i] = counter;
      counter++;
    }
    endRow--;

    for (let i = endRow; i >= startRow; i--) {
      result[i][startColumn] = counter;
      counter++;
    }
    startColumn++;
  }
  return result;
}