getElementsByClassName VS querySelectorAll

JavaScript performance comparison

Revision 36 of this test case created by Eamon Nerbonne

Info

Note that these results are very hard to interpret because jsperf plots ops/sec rather than sec/ops meaning that a few virtually instantaneous built-ins skew the scale of the below graphs.

Previous message: I wanted to see how well does jQuery performs on class selectors .. and boy, it was such a dissapointment

Preparation code

<script src="//ajax.googleapis.com/ajax/libs/jquery/2.0.0/jquery.min.js">
</script>
<div>
  <ul>
    <li>
      <a href="#" name="name" class="classname">item 1</a>
    </li>
    <li>
      <a href="#" name="name" class="classname">item 2</a>
    </li>
    <li>
      <a href="#" name="name" class="classname">item 3</a>
    </li>
    <li>
      <a href="#" name="name" class="classname">item 4</a>
    </li>
    <li>
      <a href="#" name="name" class="classname">item 5</a>
    </li>
    <li>
      <a href="#" name="name" class="classname">item 6</a>
    </li>
    <li>
      <a href="#" name="name" class="classname">item 7</a>
    </li>
    <li>
      <a href="#" name="name" class="classname">item 8</a>
    </li>
    <li>
      <a href="#" name="name" class="classname">item 9</a>
    </li>
    <li>
      <a href="#" name="name" class="classname">item 10</a>
    </li>
  </ul>
</div>
<div id="someid"></div>
<script>
  var nodes;
</script>

Preparation code output

Test runner

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Testing in unknown unknown
Test Ops/sec
getElementsByClassName
nodes = document.getElementsByClassName('classname');
pending…
querySelectorAll
nodes = document.querySelectorAll('.classname');
pending…
jQuery $(.class)
nodes = $(".classname");
pending…
querySelector
nodes = document.querySelector('.classname');
pending…
QuerySelectorAll ID
nodes = document.querySelectorAll('#someid');
pending…
GetElementById
nodes = document.getElementById("someid");
pending…

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Revisions

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