function transform(fn, arr) {
    let result = [];
    for (let el of arr) {
        result.push(fn(el)); // We push the result of the transformed item to result
    }
    return result;
}
console.log(transform(x => x * 2, [1,2,3,4])); // [2, 4, 6, 8]
As you can see, our transform fun...