Bangladesh Mobile Number Validation Using JavaScript

C# Control
=========

<asp:TextBox ID="txtSMSNotification" class="input-semi-large" runat="server" onchange="ValidateMobNumber();"></asp:TextBox>

JavaScript Control
==============

<script type="text/javascript">

        function ValidateMobNumber() {

            var fld = document.getElementById("ContentPlaceHolder_txtSMSNotification");

            if (fld.value == "") {

                alert("You didn't enter a sms notification number.");

                fld.value = "";

                fld.focus();

                return false;

            }

            var mySplitResult = fld.value.substring(0, 2);

            if (mySplitResult != "01") {

                alert("Not in correct format");

                fld.value = "";

                fld.focus();

                return false;

            }

            if (isNaN(fld.value)) {

                alert("SMS notification number contains illegal characters.");

                fld.value = "";

                fld.focus();

                return false;

            }

            if (!(fld.value.length == 11)) {

                alert("SMS notification number is the wrong length. \nPlease enter 11 digit mobile no.");

                fld.value = "";

                fld.focus();

                return false;

            }

        }

           

    </script>