idk

deepFlat.js

let a = [1, 2, [3, [4, [5, [6], [7, [8]]]]]];

function brainDeadDeepFlat(arr)
{
	return Array.isArray(arr)
		? arr.reduce( (arr, e) => arr.concat(brainDeadDeepFlat(e)), [] )
		: [arr];
}

function normalBrainDeepFlat(arr)
{
	return arr.some(e => Array.isArray(e))
		? bigBrainDeepFlat(arr.flat())
		: arr;
}

function galaxyBrainDeepFlat(arr)
{
	return arr.flat(Number.MAX_VALUE);
}

function transcedentalBrainDeepFlat(arr)
{
	return arr.toString().split(',').map(e => +e);
}

console.log(transcedentalBrainDeepFlat(a));