In react, If we want to use Toast, Firstly, We need to import a ReactElement in render function.
Actually, It's so complex.Now, You can use react-toast-awesome to your your code which you want to show toast.
PS:It's mounted in body of HTML

npm install react-toast-awesome

import $message from 'react-toast-awesome';

$message.success(string:<message>);

• message.info(<string|ReactElement>)
• message.success(<string|ReactElement>)
• message.error(<string|ReactElement>)
• message.warning(<string|ReactElement>)