Validate Phone Number

In this blog, I am going to explain about validating phone number text box in ASP.NET using Java Script.

Create a Text Box control, given below.

<asp:TextBox ID="txtPhoneNumber" runat="server" Height="18px" Width="129px"

                        onchange = "this.value = ValidatePhone(this);"></asp:TextBox>

onchange() is used to call a JavaScript function, named as ValidatePhone(). Pass the TextBox control as an argument.

I use Regular Expression to validate phone number. Java Script function could be

function ValidatePhone(phonenumber) {

    var regex = /^\(?([2-9][0-8][0-9])\)?[-. ]?([2-9][0-9]{2})[-. ]?([0-9]{4})$/;

    if (regex.test(phonenumber.value)) {

        var newPhoneNumber = phonenumber.value.replace(regex, "($1) $2-$3");

        return newPhoneNumber;

    } else {

       

        alert(" Invalid phone number");

        return phonenumber.value;

        }

}

The basic Rules of Valid phone numbers according to the North American Numbering Plan are,

• Area codes start with a number from 2–9, followed by 0–8, and then any third digit.
• The second group of three digits, known as the central office or exchange code, starts with a number from 2–9, followed by any two digits.
• The final four digits, known as the station code, have no restrictions.

These rules can easily be implemented with a few character classes:

^\(?([2-9][0-8][0-9])\)?[-. ]?([2-9][0-9]{2})[-. ]?([0-9]{4})$

Generally, the phone number format includes 4125671234, 412-567-1234, 412.567.1234, 412 567 1234, (412) 567 1234, and all related combinations. If the phone number is valid, you can convert it to your standard format, (412) 567-1234 for maintaining consistency. This can be done by using replace() method. The replacement is ($1) $2-$3. Now the phone number will be changed into (412) 567-1234.

Happy Coding!!!