Minus quantity base on id

Question

Actually I want to minus quantity based on id .When user click button on 'A', just qunatity of 'A' should get reduced by 1. This Demo code stackblitz

HTML

<p *ngFor="let item of arrayOfArray"> 
  Name: {{item.name}} Quantity: {{item.quantity - currentIndex}} <button (click)="addItem(item)">minus Quantity</button>
</p>

Component

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;
    }
  }

Answer 1

You are doing it wrong . check this demo code

for html

<p *ngFor="let item of arrayOfArray"> 
  Name: {{item.name}} Quantity: {{item.quantity}}
  <button (click)="minusItem(item)">minus Quantity</button>
</p>

  minusItem(val){
    if(val.id){
      for (let ele of this.arrayOfArray) {
         if (ele.id === val.id){
          ele.quantity--;
          break
        }
      }
    }
  }