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

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Run details:

User agent: Mozilla/5.0 (iPhone; CPU iPhone OS 17_2_1 like Mac OS X) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/17.2 Mobile/15E148 Safari/604.1

Browser: Mobile Safari 17

Operating system: iOS 17.2.1

Device Platform: Mobile

Date tested: 2 years ago

Test name	Executions per second
✓ firstChild nextSibling	15,119,806 Ops/sec
firstElementChild nextElementChild	9,441,455 Ops/sec
childNodes foreach	5,396,724 Ops/sec
ChildNodes for (into variable)	3,128,856 Ops/sec
children (direct)	3,076,758 Ops/sec
children-- (direct)	2,369,868 Ops/sec
lastElementChild previousElementChild	1,878,038 Ops/sec
ChildNodes for-- (into variable)	1,627,285 Ops/sec
children-- (into variable)	1,159,473 Ops/sec
ChildNodes for-- (direct)	815,340 Ops/sec

Test name

Executions per second

✓ firstChild nextSibling

15,119,806 Ops/sec

firstElementChild nextElementChild

9,441,455 Ops/sec

childNodes foreach

5,396,724 Ops/sec

ChildNodes for (into variable)

3,128,856 Ops/sec

children (direct)

3,076,758 Ops/sec

children-- (direct)

2,369,868 Ops/sec

lastElementChild previousElementChild

1,878,038 Ops/sec

ChildNodes for-- (into variable)

1,627,285 Ops/sec

children-- (into variable)

1,159,473 Ops/sec

ChildNodes for-- (direct)

815,340 Ops/sec

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]; }