[EmperioAf]

function toCube(x /* number */) {
    return x*x*x;
}

function extraCube(x /* number | Array<number> */) {
    if(x instanceof Array) return x.map(toCube); // [url]https://developer.mozilla.org/ru/docs/Web/JavaScript/Reference/Global_Objects/Array/map[/url]
    return toCube(x);
}