'_$visited' property in Javascript object at the return of Obervable’s map() function

Question

I have a Webservice implemented with JAX-RS and I’m consuming it with a service(utilizando Angular 2)

Follow the service:

@Injectable()
export class ModeloService {

  constructor(private http: Http) {
  }

  getAll(): Observable<Modelo[]> {
    return this.http.get(myEnvironment.MODELO_SERVICE_PATH)
      .map(res => <Modelo[]> res.json());
  }

}

Modelo that’s my class:

export class Modelo{
  id: number;
  type: string;
  size: number;

  constructor() {

  }

}

It turns out that the function return map(), mounts the following object JavaScript, that is, it inserts this property _$visited : true:

{
  "id": 28,
  "type": "type",
  "size": null,
  "_$visited": true
}

That property "_$visited" is not part of my model there on the side of the Webservice, nor on the side of the front end, if I consume this Webservice by a Rest client (I use the Restlet Client), the returned json is the expected one or if I log the return of the res.json function itself():

{
  "id": 28,
  "type": "type",
  "size": null
}

I’d like to know first where this property comes from "_$visited" and what is the best way to get rid of it, because when I send this object to my web service again, it goes with this property.

Answer 1

This property is added by Primeng to perform some library controls. Theoretically it should not influence the sending of requests to your backend.

But if the backend is releasing exceptions saying it doesn’t know the property, you can use an annotation from your JSON library to ignore these unknown properties.

An example of Jackson’s annotation in the communication class:

@JsonIgnoreProperties(ignoreUnknown = true)

This way the library will not attempt to parse this property.