30-seconds-of-code/snippets/deep-flatten-array.md

Deep flatten array

Use recursion. Use [].concat() and the spread operator ... to flatten an array, and recursively flatten each element that is an array.

const deepFlatten = arr => [].concat(...arr.map(v => Array.isArray(v) ? deepFlatten(v) : v));
// deepFlatten([1,[2],[[3],4],5]) -> [1,2,3,4,5]