Run results for: getElementById vs querySelector vs getElementsByClassName

Run details:

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/70.0.3538.110 Safari/537.36

Browser: Chrome 70

Operating system: Windows

Device Platform: Desktop

Date tested: 5 years ago

Test name	Executions per second
getElementById	2715493.2 Ops/sec
getElementsByTagName	1150559.8 Ops/sec
querySelector	1426911.9 Ops/sec
getElementsByClassName	1159674.9 Ops/sec
getElementsByName	1321494.1 Ops/sec

HTML Preparation code:

<div id="testdiv06">
  <div id="unique06" class="unique" name="unique" data-unique="1">test</div>
</div>
<div id="testdiv05">
  <div id="unique05" class="unique" name="unique" data-unique="1">test</div>
</div>
<div id="testdiv04">
  <div id="unique04" class="unique" name="unique" data-unique="1">test</div>
</div>
<div id="testdiv03">
  <div id="unique03" class="unique" name="unique" data-unique="1">test</div>
</div>
<div id="testdiv02">
  <div id="unique02" class="unique" name="unique" data-unique="1">test</div>
</div>
<div id="testdiv01">
  <div id="unique01" class="unique" name="unique" data-unique="1">test</div>
</div>
<div id="testdiv">
  <div id="unique" class="unique" name="unique" data-unique="1">test</div>
</div>

Script Preparation code:

var i, imax;
var doc = document;

Tests:

getElementById
var test = doc.getElementById('testdiv').childNodes[0].innerHTML;
getElementsByTagName
var formelem = doc.getElementById('testdiv').getElementsByTagName('div')[0].innerHTML;
querySelector
var test = doc.getElementById('testdiv').querySelector('.unique').innerHTML;
getElementsByClassName
var test = doc.getElementById('testdiv').getElementsByClassName('unique')[0].innerHTML;
getElementsByName
var test = doc.getElementsByName('unique')[0].innerHTML;

Run results for: getElementById vs querySelector vs getElementsByClassName

Test performance of different ways of get just one particular DOM element

getElementById

getElementsByTagName

querySelector

getElementsByClassName

getElementsByName