When you call JSON.parse(str, reviver), the reviver function gets called for every key value pair, starting at the most nested, allowing you to transform say all numbers to date objects, etc.

Is there a easy way to do this on an object that already exists, that isn't just a recursive function called on all keys of the current object?

I also understand I could use JSON.parse(JSON.stringify(obj),reviver), but that feels like it could cause more problems than just using recursion.