Javascript phone number validation

Google's libphonenumber is very helpful for validation and formatting of phone numbers all over the world. It is easier, less cryptic, and more robust than using a RegEx, and it comes in JavaScript, Ruby, Python, C#, PHP, and Objective-C flavors.

phone = phone.replace(/[^0-9]/g, '');
if(phone.length != 10) { 
   alert("not 10 digits");
} else {
  alert("yep, its 10 digits");
} 

This will validate and/or correct based on your requirements, removing all non-digits.