Add active class only to the selected card

Child Component

export class ChildComponent {
  @Input() public isActive: boolean = false;
  @Output() public statClick = new EventEmitter<Event>();

  public get classes(): string[] {
    const active = this.isActive ? 'isActive' : '';
    return [active];
  }

  public onStatClick(): void {
    this.statClick.emit();
  }
}

<div class="card" [ngClass]="{ active: isActive }" (click)="onStatClick()"></div>

Parent Component

export class ParentComponent  {
  
  public activeItem: ChartStat | null = null;

  @Input() public isActive: boolean = false;

  public onStatClick(clickedItem: ChartStat): void {
    this.activeItem = clickedItem;
  }
}

<app-child
  [isActive]="item === activeItem"
  (statClick)="onStatClick(item)"
/>