The Functional Side of React

As you know, React is one of the most popular JavaScript libraries to create web-based user interfaces. Its success is due to several factors, but maybe one of them is its clean and effective approach to programming.
In the React environment, every piece of a UI is a component. Components can be composed together to create other components. The application itself is a component: a composition of components. The developer approaching React is naturally led to think of it in terms of Object-Oriented Programming. The syntax itself to define a component promotes this idea: