import { Component , EventEmitter , OnInit , Output } from '@angular/core' ; import { FormBuilder , FormGroup } from '@angular/forms' ; @ Component ( { selector : 'al-track-by-demo-form' , templateUrl : './track-by-demo-form.component.html' , } ) export class TrackByDemoFormComponent implements OnInit { @ Output ( ) public updated = new EventEmitter < boolean > ( ) ; public formGroup : FormGroup ; public ngOnInit ( ) { this . formGroup = new FormBuilder ( ) . group ( { useTrackBy : [ false ] , target : [ '' ] , replacement : [ '' ] , } ) ; } }