Run results for: Array.map().filter(Boolean) vs Array.flatMap() vs Array.reduce()

Run details:

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:106.0) Gecko/20100101 Firefox/106.0

Browser: Firefox 106

Operating system: Mac OS X 10.15

Device Platform: Desktop

Date tested: 2 years ago

Test name	Executions per second
Array.map().filter(Boolean)	93712.6 Ops/sec
Array.flatMap()	178715.2 Ops/sec
Array.reduce()	35046.8 Ops/sec

Script Preparation code:

var a1 = ['', '1231237', '', '', '', '', 'ergre', '', '', '', '', 'asdf1134', '', '', '123'];
var a2 = ['1231237', '123', '1231237', '123', '1231237', '', '123sdfsdf', 'sdfsdf'],
    result,
    a1 = a1.flatMap((s, i) => i % 2 ? a1 : a2),
    a2 = a2.flatMap((s, i) => i % 2 ? a2 : a1);

Tests:

Array.map().filter(Boolean)
result = a1.map(s => a2.includes(s) && s).filter(Boolean);
Array.flatMap()
result = a1.flatMap(s => s && a2.includes(s) ? [s] : []);
Array.reduce()
result = a1.reduce((acc, s) => (s && a2.includes(s) ? [...acc, s] : acc), []);

Run results for: Array.map().filter(Boolean) vs Array.flatMap() vs Array.reduce()

comparison of filtering out falsy values from an array

Array.map().filter(Boolean)

Array.flatMap()

Array.reduce()