Show Me the Evens - Show me the Odds

even_odd.js

const numbersGenerator = (numbers) => [].concat(...Array(numbers).keys());
const props = [
    (num) => num % 2 === 0,
    (num) => !props[0](num)
]
const result = (range, type) => numbersGenerator(range).filter(_a => props[type](_a))
console.log(result(20,0)); 
console.log(result(20,1)); 

// caso de uso
// result(20,0) => Gera um array com 20 posições e retorna todos os números pares (opção 0)
// result(20,1) => Gera um array com 20 posições e retorna todos os números ímpares (opção 1)

instruçoes.txt

# 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. 

odd_even_1.js

const numbersGenerator = (numbers) => [].concat(...Array(numbers).keys());
const props = {
    "even": (num) => (num % 2 === 0),
    "odd": (num) => !props['even'](num)
}
const result = (range, type) => numbersGenerator(range).filter(props[type])
console.log(result(20,'even')); 
console.log(result(20,'odd')); 

If that number is even, she decides to count all the even numbers...

If not, she decides to count all the odd numbers...