The last test kills me :D

Dear brothers and sisters!

I came up with a solution like this, which works mostly fine!

function numberRadix(str, num) {

    // str.toString(16);

    sol = parseInt(str, num);


    if (isNaN(sol)) {
     console.log(-1);

    return -1; } else {
        console.log(sol);

        return sol;
    }


}

But at the last extra-test it won't work:

numberRadix("ASD", 15); // -1

I know it is because "ASD" can't be converted in the 15-number system, but I won't know how to work with the S-letter. Do you maybe know how to fix this?

love

Fabian