code: function zip(arrayOfArrays) {
    return arrayOfArrays[0].map(function(_, secondIndex) {
      return arrayOfArrays.map(function(_, firstIndex) {
        return arrayOfArrays[firstIndex][secondIndex];
      });
    });
  }
docs: zip([[1, 2, 3], [4, 5, 6]]) = [[1, 4], [2, 5], [3, 6]].