getElementsByClassName VS querySelectorAll

JavaScript performance comparison

Revision 72 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>
  var nodes;
</script>
<script>
Benchmark.prototype.setup = function() {
    function getElementsByClass(classList, node) {
      var node = node || document,
        list = node.getElementsByTagName('*'),
        length = list.length,
        classArray = classList.split(/\s+/),
        classes = classArray.length,
        result = [],
        i, j
      for (i = 0; i < length; i++) {
        for (j = 0; j < classes; j++) {
          if (list[i].className.search('\\b' + classArray[j] + '\\b') != -1) {
            result.push(list[i])
            break
          }
        }
      }
   
      return result
    }
};
</script>

Preparation code output

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Testing in unknown unknown
Test Ops/sec
getElementsByClassName
nodes = document.getElementsByClassName('classname');
pending…
querySelectorAll
nodes = getElementsByClass('classname', document);
pending…

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