how to add class through ts file in angular code example

Example 1: Angular add class dynamically

<button 
  *ngFor="let button of buttons" 
  class="general" 
  (click)="ChangeScreen(button.label)" 
  [class.selected]="CurrentPage == button.label">
  {{ button.label }}
</button>

Example 2: Angular add class dynamically

buttons: Array<{label: string}> = [
    {
      label: 'Global'
    },
    {
      label: 'Maintenance'
    },
    {
      label: 'Settings'
    },
    {
      label: 'Profile'
    },
    {
      label: 'Transactions'
    }
  ]