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React applications are made out of components.

What's a component?

A component is a small, reusable chunk of code that is responsible for one job. That job is often to render some HTML.

Take a look at the code below. This code will create and render a new React component:

import React from 'react'; import ReactDOM from 'react-dom'; class MyComponentClass extends React.Component { render() { return <h1>Hello world</h1>; } }; ReactDOM.render( <MyComponentClass />, document.getElementById('app') );

A lot of that code is probably unfamiliar. However you can recognize some JSX in there, as well as ReactDOM.render().

We are going to unpack that code, one small piece at a time. By the end of this lesson, you'll understand how to build a React component!

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