getElementsByClassName VS querySelectorAll

JavaScript performance comparison

Revision 94 of this test case created by Misko Hevery

Preparation code

<div id="wrapper">
  <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 context = document.getElementById('wrapper')

};
</script>

Preparation code output

<div id="wrapper"> <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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Java applet disabled.

Testing in CCBot 2.0.0 / Other 0.0.0
Test Ops/sec
getElementsByClassName
nodes = context .getElementsByClassName('classname');
var count = 0;
for(var i=0, ii = nodes.length; i<ii; i++) {
  count += nodes[i].nodeType;
}
return count;
pending…
querySelectorAll
nodes = context .querySelectorAll('.classname');
var count = 0;
for(var i=0, ii = nodes.length; i<ii; i++) {
  count += nodes[i].nodeType;
}
return count;
pending…
getElementsByTagName
nodes = context .getElementsByTagName('a');
var count = 0;
for(var i=0, ii = nodes.length; i<ii; i++) {
  count += nodes[i].nodeType;
}
return count;
pending…
querySelectorAll tag
nodes = context .querySelectorAll('a');
var count = 0;
for(var i=0, ii = nodes.length; i<ii; i++) {
  count += nodes[i].nodeType;
}
return count;
pending…
querySelectorAll All elements
nodes = context .querySelectorAll('*');
var count = 0;
for(var i=0, ii = nodes.length; i<ii; i++) {
  count += nodes[i].nodeType;
}
return count;
pending…
getElementsByTagName
nodes = context .getElementsByTagName('*');
var count = 0;
for(var i=0, ii = nodes.length; i<ii; i++) {
  count += nodes[i].nodeType;
}
return count;
pending…

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