Memoized, naïve, recursive Fibonacci function in JavaScript

fibonacci.js

var memoize = function(fn, debug) {
    var cache = {};

    return function() {
        var arguments = [].slice.apply(arguments)
        var args = JSON.stringify(arguments);

        if(cache[args] !== undefined) {
            if(debug === true) {
                print("In cache: (" + args + ", " + cache[args] + ")");
            }
            
            return cache[args];
        } else {
            var value = fn.apply(this, arguments);
            
            if(debug === true) {
                print("Brand new: (" + args + ", " + value + ")");
            }
            cache[args] = value;
            return value;
        }
    };
};

var fibonacci = function(n) {
    return n === undefined ? 0:
           n == 0 ? 0:
           n == 1 ? 1:
           fibonacci(n-1) + fibonacci(n-2);
};

fibonacci = memoize(fibonacci, true);

print(fibonacci(10));