Transition

import { useState } from 'react';
import { useClickOutside } from '@mantine/hooks';
import { Transition, Paper, Button, Box } from '@mantine/core';

const scaleY = {
  in: { opacity: 1, transform: 'scaleY(1)' },
  out: { opacity: 0, transform: 'scaleY(0)' },
  common: { transformOrigin: 'top' },
  transitionProperty: 'transform, opacity',
};

function Demo() {
  const [opened, setOpened] = useState(false);
  const clickOutsideRef = useClickOutside(() => setOpened(false));

  return (
    <Box
      maw={200}
      pos="relative"
      style={{ display: 'flex', justifyContent: 'center', margin: 'auto' }}
    >
      <Button onClick={() => setOpened(true)}>Open dropdown</Button>
      <Transition
        mounted={opened}
        transition={scaleY}
        duration={200}
        timingFunction="ease"
        keepMounted
      >
        {(transitionStyle) => (
          <Paper
            shadow="md"
            p="xl"
            h={120}
            pos="absolute"
            top={0}
            left={0}
            right={0}
            ref={clickOutsideRef}
            style={{ ...transitionStyle, zIndex: 1 }}
          >
            Dropdown
          </Paper>
        )}
      </Transition>
    </Box>
  );
}