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

Run details:

User agent: Mozilla/5.0 (Linux; Android 10; K) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/131.0.0.0 Mobile Safari/537.36

Browser: Chrome Mobile 131

Operating system: Android

Device Platform: Mobile

Date tested: one year ago

Benchmark engine: Benchmark.js

loop with push

11K/s

reduce with push

11K/s

filter with a map

6K/s

flatMap

3K/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)