@kaliber/use-element-size

useElementSize

Read the height and width of an element

Motivation

Determines the width and height (in pixels) of an element through ResizeObserver. This is more performant and easier to use than listening to a resize event and reading the element's size through getBoundingClientRect or getComputedStyle, which run on the main thread and can trash layout. Note that the hook is only updated when the element's size changes, not when the window's size changes.

Polyfill

At the time of writing, ResizeObserver is not yet supported by all current browsers. There is a polyfill available through polyfill.io.

Using @kaliberjs/build, you can add the following argument to the polyfill() call.

{polyfill(['default', 'ResizeObserver'])}

Without, you can manually add the following script to your page (or include it in your build):

https://polyfill.io/v3/polyfill.min.js?features=ResizeObserver

Installation

yarn add @kaliber/use-element-size

Usage

Basic

import { useElementSize }  from '@kaliber/use-element-size'

function Component() {
  const elementRef = React.useRef()
  const { width, height } = useElementSize(elementRef)
  return <div ref={elementRef}>{width}px × {height}px</div>
}

Animate height

.component {
  overflow: hidden;
  transition: height 0.5s;
}

import { useElementSize } from '@kaliber/use-element-size'

export function Expand({ children, expanded }) {
  const innerRef = React.useRef(null)
  const { height } = useElementSize(innerRef)

  return (
    <div 
      className={styles.component} 
      style={{ height: expanded ? height + 'px' : '0px' }}
    >
      <div ref={innerRef}>
        {children}
      </div>
    </div>
  )
}

Disclaimer

This library is intended for internal use, we provide no support, use at your own risk. It does not import React, but expects it to be provided, which @kaliber/build can handle for you.

This library is not transpiled.