function fib(pos, fibValues) {
    if (typeof fibValues[pos] !== "undefined") {
        return fibValues[pos];
    }

    result = fib(pos - 1, fibValues) + fib(pos - 2, fibValues);
    fibValues[pos] = result;
    return result;
}

let fibValues = [1, 1];
console.log(fib(30, fibValues));