Run results for: flatMap vs reduce (concat) vs reduce (push)

Run details:

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/121.0.0.0 Safari/537.36

Browser: Chrome 121

Operating system: Windows

Device Platform: Desktop

Date tested: 2 years ago

Reduce push

17K/s

FlatMap

1K/s

Reduce concat

4/s

View exact numbers

Script Preparation code:

var arr = Array(10_000).fill(1)

Tests:

Reduce concat
arr.reduce((acc, x, index) => acc.concat(x, index % 2 ? x : []), [])
FlatMap
arr.flatMap((x, index) => [x, index % 2 && x]).filter(Boolean)
Reduce push
arr.reduce((acc, x, index) => { acc.push(x); if(index % 2) { acc.push(x) } return acc; }, [])