Run results for: getBoundingClientRect vs offset when taking into account CSS transformation

Run details:

User agent: Mozilla/5.0 (Linux; Android 11; moto g power (2021)) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/107.0.0.0 Mobile Safari/537.36

Browser: Chrome Mobile 107

Operating system: Android

Device Platform: Mobile

Date tested: 2 years ago

Test name	Executions per second
getBoundingClientRect	42851.7 Ops/sec
getLocalDOMRect	9556.9 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);