getElementsByClassName VS querySelectorAll

JavaScript performance comparison

Revision 26 of this test case created

Preparation code

<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>
<script>
Benchmark.prototype.teardown = function() {
    var nodes = document.getElementsByClassName('classname');
   
    for (var i = 0, len = nodes.length; i < len; i++) {
      nodes[i].removeAttribute("target");
    }
};
</script>

Preparation code output

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Testing in unknown unknown
Test Ops/sec
getElementsByClassName
var nodes = document.getElementsByClassName('classname');

for (var i = 0, len = nodes.length; i < len; i++) {
  nodes[i].setAttribute("target", "_blank");
}
pending…
querySelectorAll
var nodes = document.querySelectorAll('.classname');

for (var i = 0, len = nodes.length; i < len; i++) {
  nodes[i].setAttribute("target", "_blank");
}
pending…
getElementsByClassName w/ slice
var nodes = Array.prototype.slice.call(document.getElementsByClassName('classname'));

for (var i = 0, len = nodes.length; i < len; i++) {
  nodes[i].setAttribute("target", "_blank");
}
pending…

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