Run results for: Fastest way to list children: childNodes vs children vs firstChild/nextSibling vs firstElementChild/nextElementSibling v2

Result: firstElementChild is the fastest yielding 3-4X performance. With lastElementChild close 2nd. Other observations: doing for loop i-- with children shows ~150% higher performance vs i++. And unloading it into a variable prior yields another ~200% boost

Go to the benchmark

Run details:

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:97.0) Gecko/20100101 Firefox/97.0

Browser: Firefox 97

Operating system: Windows

Device Platform: Desktop

Date tested: 2 years ago

Test name	Executions per second
childNodes foreach	512732.3 Ops/sec
children (direct)	712561.0 Ops/sec
firstChild nextSibling	1347092.1 Ops/sec
firstElementChild nextElementChild	4335305.0 Ops/sec
ChildNodes for (into variable)	560714.7 Ops/sec
children-- (direct)	1131146.1 Ops/sec
ChildNodes for-- (into variable)	705779.6 Ops/sec
ChildNodes for-- (direct)	1031563.2 Ops/sec
lastElementChild previousElementChild	4173133.0 Ops/sec
children-- (into variable)	1728064.0 Ops/sec

HTML Preparation code:

<html>

<body>
    <div id='test'>
        <div name='a'></div>
        <div name='b'></div>
        <div name='c'></div>
    </div>
</body>

</html>

Script Preparation code:

var parent = document.getElementById('test');

Tests:

childNodes foreach
parent.childNodes.forEach(function (node) { let n = node; });
children (direct)
for (let i = 0; i < parent.children.length; i++) { let n = parent.children[i]; }
firstChild nextSibling
let elem = parent.firstChild; do { let n = elem; } while (elem = elem.nextSibling)
firstElementChild nextElementChild
let elem = parent.firstElementChild; do { let n = elem; } while (elem = elem.nextElementSibling)
ChildNodes for (into variable)
let children = parent.childNodes; for (let i = 0; i < children.length; i++) { let n = children[i]; }
children-- (direct)
for (let i = parent.children.length-1; i >= 0; i--) { let n = parent.children[i]; }
ChildNodes for-- (into variable)
for (let i = parent.childNodes.length-1; i >= 0; i--) { let n = parent.childNodes[i]; }
ChildNodes for-- (direct)
let children = parent.childNodes; for (let i = children.length-1; i >= 0; i--) { let n = children[i]; }
lastElementChild previousElementChild
let elem = parent.lastElementChild; do { let n = elem; } while (elem = elem.previousElementSibling)
children-- (into variable)
let children = parent.children for (let i = children.length-1; i >= 0; i--) { let n = children[i]; }

Run results for: Fastest way to list children: childNodes vs children vs firstChild/nextSibling vs firstElementChild/nextElementSibling v2

Result: firstElementChild is the fastest yielding 3-4X performance. With lastElementChild close 2nd. Other observations: doing for loop i-- with children shows ~150% higher performance vs i++. And unloading it into a variable prior yields another ~200% boost

childNodes foreach

children (direct)

firstChild nextSibling

firstElementChild nextElementChild

ChildNodes for (into variable)

children-- (direct)

ChildNodes for-- (into variable)

ChildNodes for-- (direct)

lastElementChild previousElementChild

children-- (into variable)