getElementsByClassName VS querySelectorAll

JavaScript performance comparison

Revision 227 of this test case created by Carlos Ouro

Preparation code

<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.8.1/jquery.min.js">
</script>
<div id="#bar">
  <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 queryByIdRegex = /^\#[^\s]+$/
  var queryByClassnameRegex = /^\.-?[_a-zA-Z]+[_a-zA-Z0-9-]*$/
  
  function optimalSelector(selector){
          if (queryByIdRegex.test(selector)){
              var el = document.getElementById(selector.substring(1));
              return el !== null ? [el] : []
          } if(queryByClassnameRegex.test(selector)) {
              return document.getElementsByClassName(selector.substring(1))
          } else {
              return document.querySelectorAll(selector)
          }
      }

};
</script>

Preparation code output

<div id="#bar"> <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
optimalSelector (id)
nodes = optimalSelector('#bar');
pending…
getElementById
nodes = document.getElementById('bar');
pending…
querySelectorAll (class)
nodes = document.querySelectorAll('.classname');
pending…
optimalSelector (class)
nodes = optimalSelector('.classname');
pending…
optimalSelector (composed)
nodes = optimalSelector('ul li');
pending…
querySelectorAll (id)
nodes = document.querySelectorAll('#bar');
pending…
getElementsByClassName
nodes = document.getElementsByClassName('classname');
pending…
querySelectorAll (composed)
nodes = document.querySelectorAll('ul li');
pending…

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Revisions

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