свойство duration

Object? duration

переопределяет

Реализация

@Returns('num|String|Null')
Object? get duration native;

void duration=(Object? value)

set duration(Object? value) native;

© 2012 the Dart project authors
Licensed under the BSD 3-Clause "New" or "Revised" License.
https://api.dart.dev/stable/2.19.6/dart-html/AnimationEffectTiming/duration.html