Function transition

packages/animations/src/animation_metadata.ts:1092–1105

(
  stateChangeExpr:
    | string
    | ((
        fromState: string,
        toState: string,
        element?: any,
        params?: {[key: string]: any},
      ) => boolean),
  steps: AnimationMetadata | AnimationMetadata[],
  options: AnimationOptions | null = null,
)

 * @deprecated 20.2 Use `animate.enter` or `animate.leave` instead. Intent to remove in v23
 **/
export function transition(
  stateChangeExpr:
    | string
    | ((
        fromState: string,
        toState: string,
        element?: any,
        params?: {[key: string]: any},
      ) => boolean),
  steps: AnimationMetadata | AnimationMetadata[],
  options: AnimationOptions | null = null,
): AnimationTransitionMetadata {
  return {type: AnimationMetadataType.Transition, expr: stateChangeExpr, animation: steps, options};
}

/**
 * Produces a reusable animation that can be invoked in another animation or sequence,