Benchmark: ECMA .flat() vs Custom .flatten() (noop flatten)

Script Preparation code:

var arr =  Array(5000).fill(1);

Tests:

ECMA .flat()
function flatten(list) { return list.flat(9999) } flatten(arr);
Custom .flatten()
function flatten(list, dst) { if (dst === undefined) dst = list; for (let i = 0; i < list.length; i++) { let item = list[i]; if (Array.isArray(item)) { // we need to inline it. if (dst === list) { // Our assumption that the list was already flat was wrong and // we need to clone flat since we need to write to it. dst = list.slice(0, i); } flatten(item, dst); } else if (dst !== list) { dst.push(item); } } return dst; } flatten(arr);

Rendered benchmark preparation results:

Previous results

Test case name	Result
ECMA .flat()
Custom .flatten()

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Latest run results:

Run details: (Test run date: one year ago)

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/108.0.0.0 Safari/537.36

Browser/OS: Chrome 108 on Mac OS X 10.15.7

Test name	Executions per second
ECMA .flat()	3273.1 Ops/sec
Custom .flatten()	2438.9 Ops/sec

ECMA .flat() vs Custom .flatten() (noop flatten) (version: 0)