> You upgrade the libraries your website depends on, or add a dependency, and this new code happens to depend on that native prototype. Only you replaced it wit

> You upgrade the libraries your website depends on, or add a dependency, and this new code happens to depend on that native prototype. Only you replaced it with your custom method, and that method likely doesn't have the exact same behavior. You broke that new code and fixing this might not be trivial because uses of your custom method are sprinkled everywhere in your code. He was suggesting adding a prototype method, not replacing one. Unless the library your using is also adding prototypes, I can't think of an issue with this. Sure, if a new version of JS ends up using these names then things could break, but I'd bet this won't cause him a problem in actuality.