javascript - Regular expression to validate US phone numbers?

I'm trying to write a regular expression to validate US phone number of format

(123)123-1234 -- true
123-123-1234 -- true

every thing else in not valid.

I came up something like

 ^\(?([0-9]{3}\)?[-]([0-9]{3})[-]([0-9]{4})$

But this validates,
123)-123-1234
(123-123-1234

which is NOT RIGHT.

Answer

The easiest way to match both

^\([0-9]{3}\)[0-9]{3}-[0-9]{4}$

and

^[0-9]{3}-[0-9]{3}-[0-9]{4}$

is to use alternation ((...|...)): specify them as two mostly-separate options:

^(\([0-9]{3}\)|[0-9]{3}-)[0-9]{3}-[0-9]{4}$

By the way, when Americans put the area code in parentheses, we actually put a space after that; for example, I'd write (123) 123-1234, not (123)123-1234. So you might want to write:

^(\([0-9]{3}\) |[0-9]{3}-)[0-9]{3}-[0-9]{4}$

(Though it's probably best to explicitly demonstrate the format that you expect phone numbers to be in.)