client/src/components/Header.js

import { Box, Button, Menu, MenuItem } from '@mui/material';
import { useState } from 'react';
import { useNavigate, useParams } from 'react-router-dom';

import authManager from '../AuthManager';

export default function Header() {
  const navigate = useNavigate();
  const [anchorEl, setAnchorEl] = useState(null);
  const handleClick = (event) => setAnchorEl(event.currentTarget);
  const handleClose = () => setAnchorEl(null);
  const params = useParams();

  const goToAccountSelection = () => navigate(`/account`);
  const goToContacts = () => navigate(`/Contacts`);
  const goToAccountSettings = () => navigate(`/account/${params.accountId}/settings`);

  return (
    <Box>
      <Button aria-controls="simple-menu" aria-haspopup="true" onClick={handleClick}>
        Menu
      </Button>
      <Menu id="simple-menu" anchorEl={anchorEl} open={Boolean(anchorEl)} onClose={handleClose}>
        <MenuItem onClick={goToAccountSelection}>Change account</MenuItem>
        <MenuItem onClick={goToContacts}>Contacts</MenuItem>
        {params.accountId && <MenuItem onClick={goToAccountSettings}>Account settings</MenuItem>}
        <MenuItem onClick={() => authManager.disconnect()}>Log out</MenuItem>
      </Menu>
    </Box>
  );
}