Run results for: getBoundingClientRect vs offset

Run details:

User agent: Mozilla/5.0 (iPhone; CPU iPhone OS 18_2_1 like Mac OS X) AppleWebKit/605.1.15 (KHTML, like Gecko) CriOS/132.0.6834.78 Mobile/15E148 Safari/604.1

Browser: Chrome Mobile iOS 132

Operating system: iOS 18.2.1

Device Platform: Mobile

Date tested: one year ago

Access offset properties directly

4.9M/s

getBoundingClientRect

4.7M/s

getLocalDOMRect

1.4M/s

View exact numbers

Test name	Executions per second
✓ Access offset properties directly	4,888,560 Ops/sec
getBoundingClientRect	4,659,090 Ops/sec
getLocalDOMRect	1,363,298 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;