use-element-dimensions

React Hook to figure out DOM Element dimensions with updates

Usage

import useDimensions from "use-element-dimensions";

const Example = () => {
  const [{ width, height }, ref] = useDimensions();
  return (
    <div ref={ref}>
      The width of this div is: {width} and the height is: {height}
    </div>
  );
};

API

The first item in the tuple returned by the hook includes all properties of the latest ResizeObserverEntry for the specific element.

borderBoxSize

An object containing the new border box size of the observed element when the callback is run.

contentBoxSize

An object containing the new content box size of the observed element when the callback is run.

contentRect

A DOMRectReadOnly object containing the new size of the observed element when the callback is run. Note that this is better supported than the above two properties, but it is left over from an earlier implementation of the Resize Observer API, is still included in the spec for web compat reasons, and may be deprecated in future versions.

target

A reference to the Element or SVGElement being observed.

The DOMRect returned by target.getBoundingClientRect also lends its properties to this value.

x

The x coordinate of the DOMRect's origin.

y

The y coordinate of the DOMRect's origin.

width

The width of the DOMRect.

height

The height of the DOMRect.

top

Returns the top coordinate value of the DOMRect (has the same value as y, or y + height if height is negative.)

right

Returns the right coordinate value of the DOMRect (has the same value as x + width, or x if width is negative.)

bottom

Returns the bottom coordinate value of the DOMRect (has the same value as y + height, or y if height is negative.)

left

Returns the left coordinate value of the DOMRect (has the same value as x, or x + width if width is negative.)

Use case

There are already some hook libraries that provide dimensions on first render or even update them on window resize event, however in many cases this may not be sufficient. HTML DOM Elements can resize in response to a lot of things we don't expect, only one of which is screen size, for example:

• When animating any of the size properties.
• Setting a size properties on an encapsulating DOM Node.
• Orientation change (resize triggers in this case - or it should).

Development

Everything in this package is in src/index.ts. If you want to run an example to develop against, install parcel globally and then run parcel example/simple/index.html from the root directory of the project.

Building

Run yarn build to build for the three targets specified.

Testing

Integration tests use Cypress, because it is hard to do unit tests for hooks and viewport resizing.

Examples

The examples live in the example directory. To run any of them, make sure devDependencies are installed and run yarn parcel example/<name>/index.html.