S = {"_id": 0, "Qids": [ObjectId("1"), ObjectId("2"), ObjectId("3"), ObjectId("4")]}
Q1 = {"_id": ObjectId("1"), "Sid": ObjectId("0")}
Q2 = {"_id": ObjectId("2"), "Sid": ObjectId("0")}
Q3 = {"_id": ObjectId("3"), "Sid": ObjectId("0")}
Q4 = {"_id": ObjectId("4"), "Sid": ObjectId("0")}

$scope.Qlist = [Q1, Q2, Q3, Q4];
$scope.S = {};
$http.post('/S', $scope.S).success(function(data){
    var req_obj = {
        Sid: data._id,
        Q: {}
    };
    for (var i = 0; i<$scope.Qlist.length; i++) {
        req_obj.Q = $scope.Qlist[i];
        $http.post('/Q', req_obj);
    };
});

app.route('/Q')
    .post(users.requiresLogin, questions.hasAuthorization, questions.fillSurvey);