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You've learned that a React component is a small, reusable chunk of code that is responsible for one job, which often involves rendering HTML.

Here's another fact about components: every component must come from a component class.

A component class is like a factory that creates components. If you have a component class, then you can use that class to produce as many components as you want.

To make a component class, you use one of the methods in the React library: React.Component.

What is React.Component, and how do you use it to make a component class?

React.Component is a JavaScript class. To create your own component class, you must subclass React.Component. You can do this by using the syntax class YourComponentNameGoesHere extends React.Component {}.

JavaScript classes and subclassing are a complex topic beyond the scope of this course. If you aren't comfortable with them, here are some good resources to consult: 1 2 3 4.

Look at the code in app.js. A lot it is still unfamiliar, but you can understand more than you could before!

On line 4, you know that you are declaring a new component class, which is like a factory for building React components. You know that React.Component is a class, which you must subclass in order to create a component class of your own. You also know that React.Component is a property on the object which was returned by import React from 'react' on line 1.

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