Run results for: flatMap vs reduce vs loop filtering performance vs flat.map

Run details:

User agent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/142.0.0.0 Safari/537.36

Browser: Chrome 142

Operating system: Linux

Device Platform: Desktop

Date tested: 9 months ago

Benchmark engine: Benchmark.js

loop with push

47K/s

reduce with push

19K/s

map flat()

6K/s

flatMap

6K/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); }
map flat()
arr.flat().map((o) => o.assigned ? [o.name] : [])