JuniorTheoryCommon

What does the program print?

JavaScript

const nums = [1, 2, 3, 4];
const result = nums.filter((n) => n % 2 === 0).map((n) => n * 10);
console.log(result.join(" "));

20 40

Expecting 10 30: filter keeps the elements for which the function returns true, not the ones it drops, so the even numbers 2 and 4 stay.
Expecting 0 10 0 10: filter does not return the function's results like map — it returns the original elements that passed, here [2, 4].

JuniorTheoryCommon

JavaScript

const nums = [1, 2, 3, 4];
const result = nums.filter((n) => n % 2 === 0).map((n) => n * 10);
console.log(result.join(" "));

20 40

Expecting 10 30: filter keeps the elements for which the function returns true, not the ones it drops, so the even numbers 2 and 4 stay.
Expecting 0 10 0 10: filter does not return the function's results like map — it returns the original elements that passed, here [2, 4].