function result() {
    let f0 = 0;
    let f1 = 1;

    return function () {
        let oldf0 = f0;
        console.log(oldf0);
        let oldf1 = f1;
        console.log(oldf1)

        f0 = oldf1;
        f1 = oldf0 + oldf1;

        return f0;
    }

}

let fib = result();
fib();
fib();
fib();