resize-observer

---

useResizeObserver()

npm i @react-hook/resize-observer

---

A React hook that fires a callback whenever ResizeObserver detects a change to its size.

Features

• Uses a single ResizeObserver for tracking all elements used by the hooks. This approach is astoundingly more performant than using a ResizeObserver per element which most hook implementations do.
• Uses @juggle/resize-observer as a ponyfill when ResizeObserver isn't supported by the current browser.
• Automatically unobserves the target element when the hook unmounts.
• You don't have to wrap your callback in useCallback() because any mutations are handled by the hook.

Quick Start

Check out an example on CodeSandbox

import * as React from 'react'
import useResizeObserver from '@react-hook/resize-observer'

const useSize = (target) => {
  const [size, setSize] = React.useState()

  React.useLayoutEffect(() => {
    setSize(target.current.getBoundingClientRect())
  }, [target])

  // Where the magic happens
  useResizeObserver(target, (entry) => setSize(entry.contentRect))
  return size
}

const App = () => {
  const target = React.useRef(null)
  const size = useSize(target)
  return (
    <pre ref={target}>
      {JSON.stringify({width: size.width, height: size.height}, null, 2)}
    </pre>
  )
}

API

useResizeObserver(target, callback)

function useResizeObserver<T extends HTMLElement>(
  target: React.RefObject<T> | T | null,
  callback: UseResizeObserverCallback
): ResizeObserver

Argument	Type	Required?	Description
target	React.RefObject | T | null	Yes	A React ref created by useRef() or an HTML element
callback	UseResizeObserverCallback	Yes	Invoked with a single ResizeObserverEntry any time the target resizes

Types

UseResizeObserverCallback

export type UseResizeObserverCallback = (
  entry: ResizeObserverEntry,
  observer: ResizeObserver
) => any

LICENSE

MIT