With Dinero.js you can build your own “money” data-structure all right out of the box. Dinero.js always returns a new object as the result of a manipulation, making it immutable which is a lot safer.
Dinero.js carries its own currency and makes sure you can’t perform illegal manipulations (add dollars and euros for example), etc. It comes with a whole set of additional methods and assertions related to the business logic of a monetary entity.