In the following example, a container element wraps a list of items stamped out by an @for block. The container element contains an animation trigger that will later be set to query for each of the inner items.

Each time items are added, the opacity fade-in animation runs, and each removed item is faded out. When either of these animations occur, the stagger effect is applied after each item's animation is started.

<!-- list.component.html -->
<button (click)="toggle()">Show / Hide Items</button>
<hr />
<div [@listAnimation]="items.length">
  @for(item of items; track $index) {
     <div>{{ item }}</div>
  }
</div>

Here is the component code:

import {trigger, transition, style, animate, query, stagger} from '@angular/animations';
@Component({
  templateUrl: 'list.component.html',
  animations: [
    trigger('listAnimation', [
    ...
    ])
  ]
})
class ListComponent {
  items = [];

  showItems() {
    this.items = [0,1,2,3,4];
  }

  hideItems() {
    this.items = [];
  }

  toggle() {
    this.items.length ? this.hideItems() : this.showItems();
   }
 }

Here is the animation trigger code:

trigger('listAnimation', [
  transition('* => *', [ // each time the binding value changes
    query(':leave', [
      stagger(100, [
        animate('0.5s', style({ opacity: 0 }))
      ])
    ]),
    query(':enter', [
      style({ opacity: 0 }),
      stagger(100, [
        animate('0.5s', style({ opacity: 1 }))
      ])
    ])
  ])
])