unsubscribe-01.ts

import { Component, OnDestroy, OnInit } from '@angular/core';
import { Observable, Subscription } from 'rxjs';

export class RxJSUtil {
  static unsubscribe = (subscriptions: Subscription[]) =>
    subscriptions.forEach(subscription => subscription.unsubscribe());
}

@Component({
  selector: 'nx-tutorial-root',
  templateUrl: './app.component.html',
  styleUrls: ['./app.component.scss']
})
export class AppComponent implements OnInit, OnDestroy {
  @Selector(CustomersState.SelectedCustomer)
  private selectedCustomer$: Observable<Customer>;

  @Selector(OrdersState.NewOrder)
  private newOrder$: Observable<Order>;

  private subscriptions: Subscription[];

  constructor() {
    this.subscriptions = [];
  }

  ngOnInit() {
    this.subscriptions.push(
      this.selectedCustomer$.subscribe(customer => {
        // Do something
      }),
      this.newOrder$.subscribe(order => {
        // Do something
      })
    );
  }

  ngOnDestroy() {
    RxJSUtil.unsubscribe(this.subscriptions);
  }
}