The React add-ons are a collection of useful utility modules for building React apps. These should be considered experimental and tend to change more often than the core.
TransitionGroup and CSSTransitionGroup, for dealing with animations and transitions that are usually not simple to implement, such as before a component's removal.
LinkedStateMixin, to simplify the coordination between user's form input data and the component's state.
cloneWithProps, to make shallow copies of React componen