Validate phone number using javascript

Question

I'm trying to validate phone number such as 123-345-3456 and (078)789-8908 using JavaScript. Here is my code

function ValidateUSPhoneNumber(phoneNumber) {   var regExp = /^(\([0-9]{3}\) |[0-9]{3}-)[0-9]{3}-[0-9]{4}/;   var phone = phoneNumber.match(regExp);   if (phone) {     alert('yes');     return true;   }   alert('no');   return false; } 

I'm testing the function using ValidateUSPhoneNumber('123-345-34567') which has 5 digits before the last hyphen which is invalid as per regex. But the function returns true. Can any one explain why?

Answer 1

JavaScript to validate the phone number:

function phonenumber(inputtxt) {    var phoneno = /^\(?([0-9]{3})\)?[-. ]?([0-9]{3})[-. ]?([0-9]{4})$/;    if(inputtxt.value.match(phoneno)) {      return true;    }    else {      alert("message");      return false;    }  }

The above script matches:

XXX-XXX-XXXX
XXX.XXX.XXXX
XXX XXX XXXX

If you want to use a + sign before the number in the following way
+XX-XXXX-XXXX
+XX.XXXX.XXXX
+XX XXXX XXXX
use the following code:

function phonenumber(inputtxt) {   var phoneno = /^\+?([0-9]{2})\)?[-. ]?([0-9]{4})[-. ]?([0-9]{4})$/;   if(inputtxt.value.match(phoneno)) {     return true;   }     else {       alert("message");     return false;   } } 

Answer 2

This regular expression /^(\([0-9]{3}\)\s*|[0-9]{3}\-)[0-9]{3}-[0-9]{4}$/ validates all of the following:

'123-345-3456'; '(078)789-8908'; '(078) 789-8908'; // Note the space 

To break down what's happening:

1. The group in the beginning validates two ways, either (XXX) or XXX-, with optionally spaces after the closing parenthesis.
2. The part after the group checks for XXX-XXX