JSX is the syntax extension for JavaScript. It is not mandatory to use JSX with React, but there are some benefits that make development easier. JSX, for example, prevents injection attacks because all values are escaped in the JSX before they are rendered. The most useful feature is that you can embed JavaScript expressions in the JSX by wrapping it with curly brackets; this technique will be used a lot in the following chapters. In the following example, we can access the component props when using JSX. The component props are covered in the next section:

class Hello extends React.Component {
  render() {
    return <h1>Hello World {this.props.user}</h1>;
  }
}

You can also pass a JavaScript expression as props, as shown in the following code:

<Hello count={2+2} />

JSX is compiled to the React.createElement() calls by Babel. You can use both internal...