Definition of a Component

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(...