Run results for: flatMap vs reduce vs loop filtering vs filter/map performance

Run details:

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/134.0.0.0 YaBrowser/25.4.0.0 Safari/537.36

Browser: Yandex Browser 25

Operating system: Mac OS X 10.15.7

Device Platform: Desktop

Date tested: one year ago

Benchmark engine: Benchmark.js

reduce with push

18K/s

loop with push

17K/s

filter with a map

14K/s

flatMap

5K/s

View exact numbers

Script Preparation code:

var arr = Array.from({length:10000}, (v, i) => ({name: i, assigned: Math.random() < 0.5}));

Tests:

flatMap
arr.flatMap((o) => (o.assigned ? [o.name] : []));
reduce with push
arr.reduce((a, o) => (o.assigned && a.push(o.name), a), [])
loop with push
{ const a = []; for (const o of arr) if (o.assigned) a.push(o.name); }
filter with a map
arr.filter(item => item.assigned).map(item => item.name)