getElementsByClassName VS querySelectorAll

JavaScript performance comparison

Revision 167 of this test case created by

Preparation code

<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.8.1/jquery.min.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() {
  function domFunc(selector) {
    var m = 0;
  
    if (selector.indexOf(' ') === -1) {
      var i = selector[0];
      m = selector.indexOf('[name=') > -1 ? 4 : (i === '.' ? 1 : (i === '#' ? 2 : 3));
    }
  
    return ['querySelector', 'getElementsByClassName', 'getElementById', 'getElementsByTagName', 'getElementsByName'][m];
  }
  
  function find(selector, context) {
    var method = domFunc(selector);
    if (method.indexOf('get') > -1) {
      selector = method === 'getElementsByName' ? /([^'"=\]]*)[\]]/g.exec(selector)[1] : selector.substr(1);
    }
    return (context || document)[method](selector);
  }
  
  function find2(selector, context, first) {
    context = context || document;
    var m;
  
    if( m = /^([.#])?(\w+)$/.exec(selector) ) {
      if(m[1] === '#') { return context.getElementById(m[2]); }
      var elms = context['getElementsBy' + (m[1] === '.' ? 'Class' : 'Tag') + 'Name'](m[2]);
      return first ? elms[0] : elms;
    } else if( m = /^[\[]name=["']?([^'"\]]+)["']?[\]]$/i.exec(selector) ) {
      var elms = context.getElementsByName(m[1]);
      return first ? elms[0] : elms;
    }
  
    return context['querySelector' + (first ? '' : 'All')](selector);
  }

};
</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
nodes = document.getElementsByClassName('classname').length;
pending…
querySelectorAll
nodes = document.querySelectorAll('.classname').length;
pending…
jQuery $(.class)
nodes = $(".classname").length;
pending…
querySelector
nodes = document.querySelector('.classname').length;
pending…
custom find()
nodes = find('.classname').length
pending…
custom find() - force querySelector
nodes = find('.classname ').length
pending…
cutom find2() - regex method
nodes = find2('.classname').length
pending…

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Revisions

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