XAService.service.ts

import { BehaviorSubject } from 'rxjs';
import { Injectable } from '@angular/core';

@Injectable({
    providedIn: 'root'
})
export class XAService {

    // private selectedXA = new BehaviorSubject<string>(null);
    // xa$ = this.selectedXA.asObservable();

    selectedXA: string;

    changeXA(xa: string) {
        this.selectedXA = xa;
    }
}