I have a array of objects to check from that primary is true is only one time on the checkbox otherwise show alert

Question

I have a array of objects to check from that primary is true is only one time on the checkbox otherwise show alert see image below:-

 <mat-checkbox class="example-margin" [(ngModel)]="primary" formControlName="primary"> Make this primary </mat-checkbox>

In this array of object there are 2 primary = true in that

Answer 1

Suppose your array is data .

let primaryGuys = data.filter(person => person.primary === true);
if(primaryGuys >1) {
   alert('HEY!')
}