计算使用angular 6勾选了多少个复选框

selectedCheckboxes: boolean[] = [false, false, false, false];

<input type="checkbox" [(ngModel)]="selectedCheckboxes[0]">
<input type="checkbox" [(ngModel)]="selectedCheckboxes[1]">
<input type="checkbox" [(ngModel)]="selectedCheckboxes[2]">
<input type="checkbox" [(ngModel)]="selectedCheckboxes[3]">

getSelectedCheckboxCount(): number {
  return this.selectedCheckboxes.filter(checkbox => checkbox).length;
}