Run results for: lodash flattenDeep vs js native

Run details:

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/102.0.0.0 Safari/537.36

Browser: Chrome 102

Operating system: Windows

Device Platform: Desktop

Date tested: one year ago

Test name	Executions per second
_.flattenDeep	2830457.0 Ops/sec
// Native	304901.5 Ops/sec
Native(ES2019)	739809.1 Ops/sec
native 2	236470.7 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