getElementsByClassName VS querySelectorAll

JavaScript performance comparison

Revision 140 of this test case created by CSS style setter

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

<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>

Test runner

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Testing in CCBot 2.0.0 / Other 0.0.0
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…
getElementsByClassName reverse
var nodes = document.getElementsByClassName('classname');

var l = nodes.length - 1;
for (var i = l; i >= 0; i--) {
  nodes[i].setAttribute("target", "_blank");
}
pending…

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Revisions

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