JAVASCRIPT

react classname

render() {
  return <span className="menu navigation-menu">Menu</span>
}

react class names

<div className="aClass"> </div>
/*NOT*/
<div class="aClass"></div>

JSX className

// In JSX, you can’t use the word class! You have to use className instead. This is because JSX gets translated into JavaScript, and class is a reserved word in JavaScript.

// When JSX is rendered, JSX className attributes are automatically rendered as class attributes.
// When rendered, this JSX expression...
const heading = <h1 className="large-heading">Codecademy</h1>;

// ...will be rendered as this HTML
<h1 class="large-heading">Codecademy</h1>