yarn add react-use-measure

This small tool will measure the boundaries (for instance width, height, top, left) of a view you reference. It is reactive and responds to changes in size, window-scroll and nested-area-scroll.

Why do we need this hook?

Because there is no simple way to just get relative view coordinates. Yes, there is getBoundingClientRect, but it does not work when your content sits inside scroll areas whose offsets are simply neglected (as well as page scroll). Worse, mouse coordinates are relative to the viewport (the visible rect that contains the page). There is no easy way, for instance, to know that the mouse hovers over the upper/left corner of an element. This hook solves it for you.

You can try a live demo here: https://codesandbox.io/s/musing-kare-4fblz

Usage

1import useMeasure from 'react-use-measure'
2
3function App() {
4  const [ref, bounds] = useMeasure()
5
6  // consider that knowing bounds is only possible *after* the view renders
7  // so you'll get zero values on the first run and be informed later
8
9  return <div ref={ref} />
10}

Api

1interface RectReadOnly {
2  readonly x: number
3  readonly y: number
4  readonly width: number
5  readonly height: number
6  readonly top: number
7  readonly right: number
8  readonly bottom: number
9  readonly left: number
10}
11
12type Options = {
13  // Debounce events in milliseconds
14  debounce?: number | { scroll: number; resize: number }
15  // React to nested scroll changes, don't use this if you know your view is static
16  scroll?: boolean
17  // You can optionally inject a resize-observer polyfill
18  polyfill?: { new (cb: ResizeObserverCallback): ResizeObserver }
19  // Measure size using offsetHeight and offsetWidth to ignore parent scale transforms
20  offsetSize?: boolean
21}
22
23useMeasure(
24  options: Options = { debounce: 0, scroll: false }
25): [React.MutableRefObject<HTMLElement | SVGElement>, RectReadOnly]

⚠️ Notes

Resize-observer polyfills

This lib relies on resize-observers. If you need a polyfill you can either polute the window object or inject it cleanly using the config options. We recommend @juggle/resize-observer.

1import { ResizeObserver } from '@juggle/resize-observer'
2
3function App() {
4  const [ref, bounds] = useMeasure({ polyfill: ResizeObserver })

Multiple refs

useMeasure currently returns its own ref. We do this because we are using functional refs for unmount tracking. If you need to have a ref of your own on the same element, use react-merge-refs.