Function runLeaveAnimations

packages/core/src/render3/instructions/animation.ts:280–310

(
  lView: LView,
  tNode: TNode,
  value: string | AnimationClassBindingFn,
  ngZone: NgZone,
)

}

function runLeaveAnimations(
  lView: LView,
  tNode: TNode,
  value: string | AnimationClassBindingFn,
  ngZone: NgZone,
): {promise: Promise<void>; resolve: VoidFunction} {
  const {promise, resolve} = promiseWithResolvers<void>();
  const nativeElement = getNativeByTNode(tNode, lView) as Element;

  ngDevMode && assertElementNodes(nativeElement, 'animate.leave');

  const renderer = lView[RENDERER];
  allLeavingAnimations.add(lView[ID]);
  (getLViewLeaveAnimations(lView).get(tNode.index)!.resolvers ??= []).push(resolve);

  const activeClasses = getClassListFromValue(value);
  if (activeClasses && activeClasses.length > 0) {
    animateLeaveClassRunner(
      nativeElement as HTMLElement,
      tNode,
      lView,
      activeClasses,
      renderer,
      ngZone,
    );
  } else {
    resolve();
  }

  return {promise, resolve};
}

/**
 * This function actually adds the classes that animate element that's leaving the DOM.