Run results for: lodash flattenDeep vs js native

Run details:

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:95.0) Gecko/20100101 Firefox/95.0

Browser: Firefox 95

Operating system: Mac OS X 10.15

Device Platform: Desktop

Date tested: 2 years ago

Test name	Executions per second
_.flattenDeep	4881203.5 Ops/sec
// Native	810792.6 Ops/sec
Native(ES2019)	6859929.5 Ops/sec
native 2	1329187.8 Ops/sec

HTML Preparation code:

<script type="text/javascript" src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.11/lodash.js"></script>

Script Preparation code:

var elements = [1, [2, [3, [4]], 5]];

const flattenDeep = (arr) => Array.isArray(arr)
  ? arr.reduce( (a, b) => a.concat(flattenDeep(b)) , [])
  : [arr];

const flattenDeepL = (arr) => arr.flatMap((subArray, index) => Array.isArray(subArray) ? flattenDeepL(subArray) : subArray);

Tests:

_.flattenDeep
_.flattenDeep(elements);
// Native
const flattenDeep = (arr) => Array.isArray(arr) ? arr.reduce( (a, b) => a.concat(flattenDeep(b)) , []) : [arr]; flattenDeep(elements)
Native(ES2019)
elements.flat(Infinity)
native 2
const flattenDeep = (arr) => arr.flatMap((subArray, index) => Array.isArray(subArray) ? flattenDeep(subArray) : subArray) flattenDeep(elements)

Run results for: lodash flattenDeep vs js native

_.flattenDeep

// Native

Native(ES2019)

native 2