JuniorTheoryCommon

What does the program print?

JavaScript

const twice = (x) => {
    x * 2;
};

console.log(twice(4));

undefined

Expecting 8, as from (x) => x * 2: once the body is in braces, only return gives a value back, and without it the call returns undefined.
Expecting null from a function that returns nothing: a call without return always gives undefined; null appears only when it is set on purpose.

JuniorTheoryCommon

JavaScript

const twice = (x) => {
    x * 2;
};

console.log(twice(4));

undefined

Expecting 8, as from (x) => x * 2: once the body is in braces, only return gives a value back, and without it the call returns undefined.
Expecting null from a function that returns nothing: a call without return always gives undefined; null appears only when it is set on purpose.