Run results for: flatMap vs reduce vs loop filtering performance

Run details:

User agent: Mozilla/5.0 (iPhone; CPU iPhone OS 18_0 like Mac OS X) AppleWebKit/605.1.15 (KHTML, like Gecko) CriOS/130.0.6723.90 Mobile/15E148 Safari/604.1

Browser: Chrome Mobile iOS 130

Operating system: iOS 18.0

Device Platform: Mobile

Date tested: one year ago

Benchmark engine: Benchmark.js

loop with push

23K/s

reduce with push

18K/s

flatMap

5K/s

View exact numbers

Test name	Executions per second
✓ loop with push	23,048 Ops/sec
reduce with push	18,206 Ops/sec
flatMap	4,833 Ops/sec

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); }

Run results for: flatMap vs reduce vs loop filtering performance

https://stackoverflow.com/a/77247681

flatMap

reduce with push

loop with push