Run results for: querySelector vs getElementsByClassName[0] with real dom

Run details:

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/74.0.3729.131 Safari/537.36

Browser: Chrome 74

Operating system: Windows

Device Platform: Desktop

Date tested: 4 years ago

Test name	Executions per second
querySelector	2556672.0 Ops/sec
getElementsByClassName	2262065.0 Ops/sec

HTML Preparation code:

<h1> Hello world</h1>
<h2>Sub title </h2>
<tr>
  <td></td>
  
  <td></td>
  
  <td></td>
  
  <td></td>
  <td></td>
  <td></td>
  <td></td>
  <td></td>
  <td></td>
  <td></td>
  <td></td>
  <td></td>
  <td></td>
  <td></td>
  
  <td></td>
  <td></td>
  
  <td></td>
</tr>
<div class="test"></div><div class="test"></div>

Tests:

querySelector
document.querySelector(".test")
getElementsByClassName
document.getElementsByClassName(".test")[0]

Run results for: querySelector vs getElementsByClassName[0] with real dom

Slight alteration because querySelector only returns a first element.

querySelector

getElementsByClassName