Пример обхода матрицы по спирали на js

matrix.js

var A = [
  [1,  2,  3,  4,  5,  6],
  [7,  8,  9,  10, 11, 12],
  [13, 14, 15, 16, 17, 18],
  [19, 20, 21, 22, 23, 24],
  [25, 26, 27, 28, 29, 30],
  [31, 32, 33, 34, 35, 36]
];

var depth = 0;
var len = A.length - 1;
var maxDepth = Math.ceil(len / 2);

iterate = function() {
  for(var i = depth; i <= len - depth; i++) {
    console.log(A[depth][i]);
  }

  for(var i = depth + 1; i <= len - depth; i++) {
    console.log(A[i][len - depth]);
  }

  for(var i = len - depth - 1; i >= depth; i--) {
    console.log(A[len - depth][i]);
  }

  for(var i = len - depth - 1; i >= depth + 1; i--) {
    console.log(A[i][depth]);
  }

  depth = depth + 1;

  if(depth <= maxDepth) iterate();
};
iterate();