useResizeObserver

Observes an element's size changes using the ResizeObserver API. The callback fires whenever the observed element's dimensions change. Used internally by the Popover component for dynamic repositioning.

Import

import { useResizeObserver } from '@andrejground/lab';

Usage

import React from 'react';
import { useResizeObserver } from '@andrejground/lab';

export default function App() {
  const [el, setEl] = React.useState<HTMLDivElement | null>(null);
  const [size, setSize] = React.useState({ width: 0, height: 0 });

  useResizeObserver({
    element: el,
    onResize: (entries) => {
      if (!entries?.[0]) return;
      const { width, height } = entries[0].contentRect;
      setSize({ width: Math.round(width), height: Math.round(height) });
    },
  });

  return (
    <div ref={setEl} style={{ resize: 'both', overflow: 'auto', padding: 16, border: '1px solid gray' }}>
      <p>Resize me!</p>
      <p>{size.width} x {size.height}</p>
    </div>
  );
}

API

useResizeObserver({ element, onResize });

Property	Type	Description
element	Element | null	The element to observe
onResize	(entries?: ResizeObserverEntry[]) => void	Callback fired on resize