Angular SSE component - detect back to online status

server-send-events.component.ts

isOnlineSubscription: Subscription;

ngOnInit() {
  ...
  this.checkIfBackToOnline();
}

ngOnDestroy() {
  ...
  this.isOnlineSubscription.unsubscribe();
}

checkIfBackToOnline() {
  this.isOnlineSubscription = fromEvent(window, 'online').subscribe(status => {
      if (status) {
        //create dummy data to trigger refresh
        let parsedUsername = this.getUsername();
        let socketEvent = new SocketEvent(parsedUsername, 'ONLINE');
        this.socketEventStorage.refreshSocketMailEventInfo([{...socketEvent, itemType: 'MESSAGE'}]);
        this.socketEventStorage.refreshSocketContactEventInfo([{...socketEvent, itemType: 'CONTACT'}]);
        this.socketEventStorage.refreshSocketCalendarEventInfo([{...socketEvent, itemType: 'CALENDAR'}]);
      }
  });
}