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. 
**/

function counting(x){
  return [...Array(x).keys()]
    .filter(even(x) ? even : odd);
}

function even(x){
	return x % 2 === 0 
}

function odd(x){
	return x % 2 === 1
}

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