HTML Form – Phone Number validation

We validate a phone number of 10 digits with no comma, no spaces, no punctuation and there will be no + sign in front the number. Simply the validation will remove all non-digits and permit only phone numbers with 10 digits. Here is the function.

function phonenumber(inputtxt)
{
  var phoneno = /^\d{10}$/;
  if((inputtxt.value.match(phoneno))
        {
      return true;
        }
      else
        {
        alert("message");
        return false;
        }
}

To valid a phone number like
XXX-XXX-XXXX
XXX.XXX.XXXX
XXX XXX XXXX
use the following code.

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;
        }
}

If we 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;
        }
}