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

Result: firstElementChild is the fastest yielding 3-4X performance. With lastElementChild close (margin of error) 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 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/95.0.4638.54 Safari/537.36

Browser: Chrome 95

Operating system: Linux

Device Platform: Desktop

Date tested: 3 years ago

Test name	Executions per second
childNodes foreach	613017.5 Ops/sec
children (direct)	982759.4 Ops/sec
children (into variable)	2547291.8 Ops/sec
children-- (direct)	1533439.4 Ops/sec
children-- (into variable)	3417670.2 Ops/sec
ChildNodes for (direct)	527120.9 Ops/sec
ChildNodes for (into variable)	1795710.9 Ops/sec
ChildNodes for-- (direct)	822558.8 Ops/sec
ChildNodes for-- (into variable)	2287524.2 Ops/sec
firstElementChild nextElementChild	9137618.0 Ops/sec
lastElementChild previousElementChild	9071572.0 Ops/sec
firstChild nextSibling	6856389.0 Ops/sec
lastChild previousSibling	6628145.0 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]; }
children (into variable)
let children = parent.children; 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]; }
children-- (into variable)
let children = parent.children; for (let i = children.length-1; i >= 0; i--) { let n = children[i]; }
ChildNodes for (direct)
for (let i = 0; i < parent.childNodes.length; i++) { let n = parent.childNodes[i]; }
ChildNodes for (into variable)
let children = parent.childNodes; for (let i = 0; i < children.length; i++) { let n = children[i]; }
ChildNodes for-- (direct)
for (let i = parent.childNodes.length-1; i >= 0; i--) { let n = parent.childNodes[i]; }
ChildNodes for-- (into variable)
let children = parent.childNodes; for (let i = children.length-1; i >= 0; i--) { let n = children[i]; }
firstElementChild nextElementChild
let elem = parent.firstElementChild; do { let n = elem; } while (elem = elem.nextElementSibling)
lastElementChild previousElementChild
let elem = parent.lastElementChild; do { let n = elem; } while (elem = elem.previousElementSibling)
firstChild nextSibling
let elem = parent.firstChild; do { let n = elem; } while (elem = elem.nextSibling)
lastChild previousSibling
let elem = parent.lastChild; do { let n = elem; } while (elem = elem.previousSibling)

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

Result: firstElementChild is the fastest yielding 3-4X performance. With lastElementChild close (margin of error) 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)

children (into variable)

children-- (direct)

children-- (into variable)

ChildNodes for (direct)

ChildNodes for (into variable)

ChildNodes for-- (direct)

ChildNodes for-- (into variable)

firstElementChild nextElementChild

lastElementChild previousElementChild

firstChild nextSibling

lastChild previousSibling