As defined in the previous chapter, components are the fundamental building blocks of React. Virtually any visual item in a user interface can be a component. From a formal point of view, we would say that a React component is a piece of JavaScript code defining a portion of a user interface.
Consider the following code in a file:
import React from 'react';
class Catalog extends React.Component {
render() {
return <div><h2>Catalog</h2></div>;
}
}
export default Catalog;
This is an ECMAScript 2015 module, defining a basic React component.
It imports the React namespace from the react module and defines the Catalog class by extending the React.Component class. The module exports the Catalog class as a default export.
The interesting part of this definition is the implementation of the render(...