Adding properties/methods to a defined property?

If I have a property created with Object.defineProperty where I want the getter to return a string, is it possible to attach methods to that string without screwing with the global String.prototype and without accidentally converting it to a generic object?

I know that sounds kind of wonky... think of it like how Element.classList works. Where Element.classList returns and array, but that array has extra properties like add/remove/toggle.

Or even just Number where it behaves as a number variable, but also has methods.

I can't seem to create that with anything that behaves like a string.

 

Nevermind, got it. As I don't need it always applied I can do so on the fly during creation, I just had to be sure to use a "new String(myString)" to make sure as to not pollute the global String object.