Method isPlaying

Extensions/TweenBehavior/TweenManager.ts:327–330

* Tween is playing. * @param identifier Unique id to identify the tween

(identifier: string)

         * @param identifier Unique id to identify the tween
         */
        isPlaying(identifier: string): boolean {
          const tween = this._tweens.get(identifier);
          return !!tween && tween.isPlaying();
        }

        /**
         * Tween has finished.