Run results for: getBoundingClientRect vs offset

Run details:

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:109.0) Gecko/20100101 Firefox/117.0

Browser: Firefox 117

Operating system: Mac OS X 10.15

Device Platform: Desktop

Date tested: one year ago

Test name	Executions per second
getBoundingClientRect	1353334.5 Ops/sec
getLocalDOMRect	690310.6 Ops/sec
Access offset properties directly	1930808.8 Ops/sec

HTML Preparation code:

<div id="el" style="transform: rotateZ(45deg)">
  <h2>Lorem ipsum dolor sit amet</h2>
</div>

Script Preparation code:

function getLocalDOMRect(el) {
  let offsetTop = 0;
  let offsetLeft = 0;
  const width = el.offsetWidth;
  const height = el.offsetHeight;
  while (el instanceof HTMLElement) {
    offsetTop += el.offsetTop;
    offsetLeft += el.offsetLeft;
    el = el.offsetParent;
  }

  return new DOMRect(offsetLeft, offsetTop, width, height);
}

const el = document.getElementById("el");

Tests:

getBoundingClientRect
const { left, right, top, bottom } = el.getBoundingClientRect();
getLocalDOMRect
const { left, right, top, bottom } = getLocalDOMRect(el);
Access offset properties directly
const { offsetWidth, offsetHeight, offsetTop } = el;

Run results for: getBoundingClientRect vs offset

getBoundingClientRect

getLocalDOMRect

Access offset properties directly