Available on js
@:optionaloptionalpseudoElement:Null<String>
@:optionaloptionalelapsedTime:Null<Float>
@:optionaloptionalcomposed:Null<Bool>
@:optionaloptionalcancelable:Null<Bool>
@:optionaloptionalbubbles:Null<Bool>
@:optionaloptionalanimationName:Null<String>