show-me.js

/**
* Show Me the Evens - Show me the Odds 
* Diana is learning to count and she just learned the difference between odds and even numbers. 
* She wants to have some fun, so she picks a random number. 
* If that number is even, she decides to count all the even numbers up to it starting from 0 up to (but not including) the input. 
* If not, she decides to count all the odd numbers up to that number starting from 1 (but not including) the input. 
**/

const counting = (x) => {
	return arrayFrom(x)
		.filter(even(x) ? even : odd)
}

const even = (x) => {
	return x % 2 == 0 
}

const odd = (x) => {
	return x % 2 == 1
}

const arrayFrom = n => {
  return Array.from({ length: n }, (el, index) => index)
}

console.log(counting(10)); //[ 0, 2, 4, 6, 8 ]
console.log(counting(11)); //[ 1, 3, 5, 7, 9 ]

Ótima solução, só que da pra se repetir menos assim:

E seria interessante usar === (só pra garantir).

@lubien Valeu!! 😄