Tooltips & Dropdown Menus with Portals

Welcome

The Overflow Problem

Positioning Strategy

const rect = triggerRef.current.getBoundingClientRect();
const top = rect.bottom + window.scrollY + 8;
const left = rect.left + window.scrollX;

Tooltip Component

function Tooltip({ content, children }) {
  const [visible, setVisible] = useState(false);
  const [pos, setPos] = useState({ top: 0, left: 0 });
  const ref = useRef();

  const show = () => {
    const r = ref.current.getBoundingClientRect();
    setPos({ top: r.bottom + window.scrollY + 4,
             left: r.left + window.scrollX });
    setVisible(true);
  };

  return (
    <span ref={ref} onMouseEnter={show} onMouseLeave={() => setVisible(false)}>
      {children}
      {visible && createPortal(
        <div style={{ position:'absolute', top: pos.top, left: pos.left }}
             className="tooltip">{content}</div>,
        document.body
      )}
    </span>
  );
}

Updating Position on Scroll & Resize

useEffect(() => {
  if (!visible) return;
  const update = () => setVisible(false);
  window.addEventListener('scroll', update, true);
  window.addEventListener('resize', update);
  return () => {
    window.removeEventListener('scroll', update, true);
    window.removeEventListener('resize', update);
  };
}, [visible]);

Dropdown Menu Architecture

Click-Outside Handler

useEffect(() => {
  if (!open) return;
  const handler = (e) => {
    if (!menuRef.current?.contains(e.target) &&
        !triggerRef.current?.contains(e.target)) {
      setOpen(false);
    }
  };
  document.addEventListener('mousedown', handler);
  return () => document.removeEventListener('mousedown', handler);
}, [open]);

Keyboard Navigation in Dropdowns

Using a Positioning Library

import { useFloating, flip, shift } from '@floating-ui/react';

const { refs, floatingStyles } = useFloating({
  middleware: [flip(), shift()],
});

Accessibility: ARIA for Tooltips

<button aria-describedby="tip1">Hover me</button>
{visible && createPortal(
  <div id="tip1" role="tooltip">Helpful text</div>,
  document.body
)}

Quick Check

Recap

Course Complete