querySelectorAll vs getElementsByTagName

JavaScript performance comparison

Revision 43 of this test case created

Info

Checking how querySelectorAll('parent child') or '.parent .child' selection performs against combinations of getElementsByTagName, getElementsByClassName and jQuery

Preparation code

<script src="//ajax.googleapis.com/ajax/libs/jquery/1/jquery.min.js"></script>
<ul class="root-ul"><li><a class="link word" href="#word">word</a>
</li><li><a class="link glass" href="#glass">glass</a>
</li><li><a class="link lorum" href="#lorum">lorum</a>
</li><li><a class="link ipsum" href="#ipsum">ipsum</a>
</li><li><a class="link dolor" href="#dolor">dolor</a>
</li><li><a class="link sit-amet" href="#sit-amet">sit-amet</a>
</li></ul>
<script>
  Benchmark.prototype.teardown = function() {
    window.console && console.log && console.log('nodes:',nodes.length, nodes);
  };
</script>

Preparation code output

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Testing in unknown unknown
Test Ops/sec
querySelectorAll
 
var root = document.querySelectorAll('ul .link'),
    nodes = [], l, i, push = Array.prototype.push;
for (i = 0, l = root.length; i < l; i++) {
  push.apply(nodes, root[i]);
}
 pending…
getElementsByTagName + getElementsByTagName
 
var root = document.getElementsByTagName('ul'),
    nodes = [], l, i, push = Array.prototype.push;
for (i = 0, l = root.length; i < l; i++) {
  push.apply(nodes, root[i].getElementsByTagName('a'));
}
 pending…
getElementsByTagName + getElementsByClassName
 
var root = document.getElementsByTagName('ul'),
    nodes = [], l, i, push = Array.prototype.push;
for (i = 0, l = root.length; i < l; i++) {
  push.apply(nodes, root[i].getElementsByClassName('link'));
}
 pending…
getElementsByClassName + getElementsByClassName
 
var root = document.getElementsByClassName('root-ul'),
    nodes = [], l, i, push = Array.prototype.push;
for (i = 0, l = root.length; i < l; i++) {
  push.apply(nodes, root[i].getElementsByClassName('link'));
}
 pending…
getElementsByClassName + getElementsByTagName
 
var root = document.getElementsByClassName('root-ul'),
    nodes = [], l, i, push = Array.prototype.push;
for (i = 0, l = root.length; i < l; i++) {
  push.apply(nodes, root[i].getElementsByTagName('a'));
}
 pending…
jQuery by CSS class
 
var nodes = jQuery('.root-ul .link');
 pending…
jQuery by Tag + class
 
var nodes = jQuery('ul .link');
 pending…
jQuery by class + Tag
 
var nodes = jQuery('.root-ul a');
 pending…

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