Run results for: getElementById + getElementByClassName vs querySelector

Run details:

User agent: Mozilla/5.0 (Windows NT 6.1; Win64; x64; rv:102.0) Gecko/20100101 Firefox/102.0

Browser: Firefox 102

Operating system: Windows 7

Device Platform: Desktop

Date tested: one year ago

Test name	Executions per second
getElementById + getElementByClass	1192407.0 Ops/sec
querySelector	817719.6 Ops/sec

HTML Preparation code:

<div id="testElement">
  <div class="testElementChild"></div>
  <div class="testElementChild"></div>
  <div class="testElementChild"></div>
  <div class="testElementChild"></div>
  <div class="testElementChild"></div>
</div>

Tests:

getElementById + getElementByClass
var el = document.getElementById('testElement'); var children = el.getElementsByClassName('testElementChild'); var length = children.length;
querySelector
var el = document.querySelector('#testElement .testElementChild'); var length = el.length;