實際上我想根據 id 減去數量。當用戶單擊“A”上的按鈕時，“A”的數量應該減少 1。此演示代碼stackblitzHTML<p *ngFor="let item of arrayOfArray">   Name: {{item.name}} Quantity: {{item.quantity - currentIndex}} <button (click)="addItem(item)">minus Quantity</button></p>成分public currentIndex = 0;  arrayOfArray = [    {id: '1', name: 'A', quantity: '12'},     {id: '2', name: 'B', quantity: '29'},    {id: '3', name: 'C', quantity: '21'},     {id: '4', name: 'D', quantity: '11'}  ]  addItem(val){    if(val.id){      this.currentIndex += 1;    }  }