Run results for: getElementById + getElementByClassName vs querySelector

Run details:

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:128.0) Gecko/20100101 Firefox/128.0

Browser: Firefox 128

Operating system: Windows

Device Platform: Desktop

Date tested: one year ago

Benchmark engine: Benchmark.js

getElementById + getElementByClass

5.7M/s

querySelector

1.1M/s

View exact numbers

Test name	Executions per second
✓ getElementById + getElementByClass	5,653,047 Ops/sec
querySelector	1,096,920 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;