react.dev/examples/introducing-jsx.js

function formatName(user) {
  return (
    user.firstName + ' ' + user.lastName
  );
}

const user = {
  firstName: 'Harper',
  lastName: 'Perez',
};

const element = (
  <h1>Hello, {formatName(user)}!</h1>
);

ReactDOM.render(
  element,
  document.getElementById('root')
);