Inserting variables and constants into tag attributes in JSX

Variables and constants can be inserted not only into tag texts, but also into attributes. In this case, quotation marks are not placed around attributes:

jsxfunction App() {
  const str = 'elem';
  
  return <div id={str}>
    text
  </div>;
}

The result of running this code will be the following:

html<div id="elem">
  text
</div>

jsxfunction App() {
  const attr = 'block';
  
  return <div>
    text
  </div>;
}