Validation for a 10 digit phone number

Question

I'm looking for a simple regex exp that will validate a 10 digit phone number. I'd like to make sure that the number is exactly 10 digits, no letters, hyphens or parens and that the first two digits do not start with 0 or 1. Can someone help out?

Answer 1

/[2-9]{2}\d{8}/

Answer 2

[2-9][2-9][0-9]{8}

Answer 3

^[2-9]{2}[0-9]{8}$

I consider [0-9] to be better to read than \d, especially considering the preceding [2-9]

The ^ and $ ensure that the input string consists ONLY of those 8 characters - otherwise it is not guaranteed that the input string is not larger - i.e. "12345678901" would match the regex w/o those two characters - although it is 11 chars and starts with a 1!