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
import useMeasure from 'react-use-measure'
function App() {
const [ref, bounds] = useMeasure()
// consider that knowing bounds is only possible *after* the view renders
// so you'll get zero values on the first run and be informed later
return <div ref={ref} />
}Api
interface RectReadOnly {
readonly x: number
readonly y: number
readonly width: number
readonly height: number
readonly top: number
readonly right: number
readonly bottom: number
readonly left: number
}
type Options = {
// Debounce events in milliseconds
debounce?: number | { scroll: number; resize: number }
// React to nested scroll changes, don't use this if you know your view is static
scroll?: boolean
// You can optionally inject a resize-observer polyfill
polyfill?: { new (cb: ResizeObserverCallback): ResizeObserver }
// Measure size using offsetHeight and offsetWidth to ignore parent scale transforms
offsetSize?: boolean
}
useMeasure(
options: Options = { debounce: 0, scroll: false }
): [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.
import { ResizeObserver } from '@juggle/resize-observer'
function App() {
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.