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.

$3

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

``jsx 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

Api

`jsx 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, RectReadOnly]`

`⚠️ Notes`

`$3`

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.

`jsx import { ResizeObserver } from '@juggle/resize-observer'

function App() { const [ref, bounds] = useMeasure({ polyfill: ResizeObserver })``

$3

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.