conditional rendering of components class in react code example

Example 1: react conditional class

<div className={"btn-group pull-right " + (this.props.showBulkActions ? 'show' : 'hidden')}>

Example 2: conditional rendering react

function Mailbox(props) {
  const unreadMessages = props.unreadMessages;
  return (
    <div>
      <h1>Hello!</h1>
      {unreadMessages.length > 0 &&        <h2>          You have {unreadMessages.length} unread messages.        </h2>      }    </div>
  );
}

const messages = ['React', 'Re: React', 'Re:Re: React'];
ReactDOM.render(
  <Mailbox unreadMessages={messages} />,
  document.getElementById('root')
);