getElementsByClassName VS querySelectorAll

JavaScript performance comparison

Revision 20 of this test case created by pavelrevers

Preparation code

<script src="//ajax.googleapis.com/ajax/libs/mootools/1.3/mootools-yui-compressed.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>
<script>
  var nodes;
</script>
<script>
  Benchmark.prototype.setup = function() {
    var App = {};
    var found = [], className, matchClass, i;
    
    var $c = function(str) {
        var nodes = document.getElementsByTagName('*');
        for (i = 0; node = nodes[i++];){
            className = node.className;
            matchClass = new RegExp('(^|\\s)'+ str +'(\\s|$)');
            if (matchClass.test(className)) found.push(node);
        }
        return found;
    };
  };
</script>

Preparation code output

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Testing in unknown unknown
Test Ops/sec
getElementsByClassName
 
nodes = $c('classname');
 pending…
querySelectorAll
 
nodes = $$('.classname');
 pending…

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