Use within an animation query() call to issue a timing gap after each queried item is animated.

Usage notes

In the following example, a container element wraps a list of items stamped out by an ngFor. 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">
  <div *ngFor="let item of items">
    {{ 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 }))
      ])
    ])
  ])
])