Deep flatten array

JavaScript, Array, Recursion · Oct 22, 2020

Deep flattens an array.

  • Use recursion.
  • Use Array.prototype.concat() with an empty array ([]) and the spread operator (...) to flatten an array.
  • 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]

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