How to properly store data after a request in a service?

Question

Angular

Good day,
I can not fully understand the services. The request to the backend passes once (as it should). But going to another page, and then returning back, the data cannot be collected correctly.
I output them to the "Data Tables" table via *ngFor. When the page is first opened, a request is made to the backend and everything is displayed and working well. But when you come to the page again, the data is visible, but on any action it disappears (for example, when trying to sort)
Component:

public dataTestServices: any;

    constructor(private servicesServices: ServicesService) {
    }

    ngOnInit() {
        this.servicesServices.getTestServices().subscribe(
            data => {
                this.dataTestServices = data.test_services;
            });
    }

service:

getTestServices() {
        return this.jsonApiService.getQuery('service/get_test');
    }

Answer 1

There is a possibility that you are assigning a new (processed) array. The link to the previous array is lost, the trash can takes away all the data - that's all and disappears. You need to work with the original or assign a new array to the component again.