how to store and print this structure -- Javascript

I would like to know how to go this structure, the identification sending and receiving students whose teachers taught them lessons

---php--

 $sql = $base->Prepare("select CodiAsig, Grupo, NombAsig, CeduEstu, NombEstu, ApelEstu
                            from  profesores as p
                            inner join asignaturas as a on p.CeduProf = a.Profesores_CeduProf
                            inner join calificaciones as c  on a.CodiAsig = c.Asignaturas_CodiAsig
                            inner join estudiantes as e on e.CeduEstu = c.Estudiantes_CeduEstu
                            where p.CeduProf =:cedula
                            order by CodiAsig, Grupo;");


$sql->Execute();
$datos = $sql->fetchAll(PDO::FETCH_ASSOC|PDO::FETCH_GROUP);
$mijsongrupos = json_encode($datos);
echo $mijsongrupos;

---javascript---

console.log(str);
var vector = (JSON.parse(str));
var len = vector.length;
console.log(vector);

{"prog1":[{"Grupo":"1","NombAsig":"programacion","CeduEstu":"1124018648","NombEstu":"pedro","ApelEstu":"pimienta"},{"Grupo":"1","NombAsig":"programacion","CeduEstu":"456789","NombEstu":"juan","ApelEstu":"pimienta"}],"prog2":[{"Grupo":"1","NombAsig":"estructura","CeduEstu":"11223344","NombEstu":"diego","ApelEstu":"vides"}]}

Object {prog1: Array[2], prog2: Array[1]}prog1: Array[2]0: Object1: Objectlength: 2__proto__: Array[0]prog2: Array[1]0: Objectlength: 1__proto__: Array[0]__proto__: Object