Run results for: getElementsByClassName vs querySelectorAll

Run details:

User agent: Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:63.0) Gecko/20100101 Firefox/63.0

Browser: Firefox 63

Operating system: Ubuntu

Device Platform: Desktop

Date tested: 5 years ago

Test name	Executions per second
getElementsByClassName	60659.4 Ops/sec
querySelectorAll	859.8 Ops/sec

HTML Preparation code:

<style>.searchMe {border: 1px sold red;}</style>
<table id="tableTest"></table>

Script Preparation code:

for(var i=0; i<10000; ++i)
{
  var cell = tableTest.insertRow(-1).insertCell(-1);
  if(i%2==0)
     cell.classList.add('searchMe');
}

Tests:

getElementsByClassName
var found = tableTest.getElementsByClassName('searchMe'); tableTest.rows[0].cells[0].textContent = found.length;
querySelectorAll
var found = tableTest.querySelectorAll('.searchMe'); tableTest.rows[0].cells[0].textContent = found.length;