Let's wrap up beginner React.js lessons with handling JS events and data changes in React.js. If you build a Reactjs app correctly, each component is able to be very "dumb"..it will only be aware of a few pieces of the application and can be reused in multiple places.
If a component is only aware of the data it needs and the event(s) it needs to fire when things change, it can be extremely decoupled from the rest of the application and less prone to break as the React JS application changes over time.