Transition

const [onOff, setOnOff] = useState(true)
 
return (
  <div>
    <button onClick={() => setOnOff(!onOff)}>toggle</button>
    <Transition state={onOff} timeout={300}>
      {({ simpleStatus, shouldMount }) => shouldMount && (
        <p style={{
          transition: '.3s',
          opacity: simpleStatus === 'enter' ? 1 : 0,
        }}
        >
          I'm fading
        </p>
      )}
    </Transition>
  </div>
)
 

function Transition(props: TransitionProps): React.ReactNode