const nums = [1, 2, 3, 4, 5];
const result = nums
  .filter(n => n % 2 !== 0)
  .map(n => n ** 2)
  .reduce((acc, n) => acc + n, 0);

const arr = [10, , 20, undefined, 30];
const mapped = arr.map(x => x * 2);

console.log(result, mapped);