I need help creating a regular expression that validates a US telephone number with or without extension.  It needs to require an area code enclosed in parentheses and separated by a space, require a dash(-) between the prefix and the number, and allow an extension up to 4 digits(ex. x1234).  Some matches and non-matches are provided below.

Match    (789) 555-1234
Match   (849) 555-1234 x1234
Match   (484) 555-8764 x1
Non-Match   789-555-7894
Non-Match   7895551234
Non-Match    (546) 555-1354 x12345
Non-Match   (345) 555-8794 x
Non-Match 756 468 4657

I've searched the net a found a few that claim to meet my requirements but under testing they all have some loophole that matches something it should not.  Any help would be greatly appreciated.
 

Hello,

Check these

Thanks, I had been just looking for a regex I could copy because it looked a bit daunting but going through some of the tutorials it isn't all that bad.  This is what I came up with if anyone else needs something like it:

\(\d{3}\)\s\d{3}-\d{4}(\s(x\d+)?){0,1}$