Matrix Rotation in JavaScript

Rotating a matrix in clock wise direction using for loops. 

Complexity Big O : n^2

This question was asked in live coding round of Frontend developer interviews in Flipkart, Walmartlabs

function rotateMatrix(matrix) {
  result = [];
  let len = matrix.length - 1;
  for (let i = len; i >= 0; i--) {
    var row = matrix[i].split('');
    if (result.length === 0) {
      result = row;
    } else {
      for (var j = 0; j < row.length; j++) {
        result[j] = result[j] + row[j];
      }
    }
  }
  return result;
}

console.log(
  rotateMatrix([
    '.........',
    '.##......',
    '..###....',
    '...###...',
    '.....###.',
    '......###',
    '.....###.',
    '...###...',
    '..###....',
    '.##......',
    '.........',
  ])
);

console.log(rotateMatrix(["a","b","c","d"])) // ["dcba"]