Kinda need to agree with Jay on this one. Even though it is functional, it is not something I would be using for my applications.

For my usage, I would probably have used a RegEx on the client side to strip out the non-numerics, and used a client side format function as well.

Phone numbers are a tricky item to format, as the ISO standard is poorly written IMHO; and, different areas of the world have different rules which need to be applied when dialing.