deepFlatten

Deep flattens an array.

Use recursion.[polyfill for Array.prototype.flat] Use Array.prototype.concat() with an empty array ([]) and the spread operator (...) to flatten an array. Recursively flatten each element that is an array.

typescript

const deepFlatten = (arr: any[]): any[] => {
  if (typeof Array.prototype.flat !== "undefined") return arr.flat(Infinity);
  return [].concat(
    ...arr.map((v: any) => (Array.isArray(v) ? deepFlatten(v) : v))
  );
};

typescript

deepFlatten([1, [2], [[3], 4], 5]); // [1, 2, 3, 4, 5]
deepFlatten([1, 2, [3, 4, [5, 6, [7, 8, [9, 10]]]]]); // [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]