jQuery class vs tag qualfied class selector (v32)

Revision 32 of this benchmark created on

Description

Just came across this article http://www.artzstudio.com/2009/04/jquery-performance-rules/ that recommends both tag qualifying class selectors as well as descending from an id for maximum jquery performance. Thought I'd test it out on his examples, because I've learned that you never want to tag qualify ids OR classes if you don't have to (similarly to CSS). However, considering the age of the article, the way jquery works could well be different now.

Preparation HTML

<div id="content">
  <form method="post" action="/">
    <h2>Traffic Light</h2>
    <ul id="traffic_light">
      <li class="red"><input type="radio" class="on" name="light" value="red" /> Red</li>
      <li class="yellow"><input type="radio" class="off" name="light" value="yellow" /> Yellow</li>
      <li class="green"><input type="radio" class="off" name="light" value="green" /> Green</li>
    </ul>
    <input class="button" id="traffic_button" type="submit" value="Go" />
  </form>
</div>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1/jquery.min.js"></script>

Setup

var $form = $('form');

Test runner

Ready to run.

Testing in
TestOps/sec
unqualified with descendant
$('.yellow input');
ready
unqualified with child
$('.yellow > input');
ready
qualified with descendant
$('li.yellow input');
ready
qualified with child
$('li.yellow > input');
ready
context unqualified with child
$('.yellow > input', $form);
ready
context qualified with child
$('li.yellow > input', $form);
ready

Revisions

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