Its working for me. Just tried the following code. Please see if you have any syntax error at your end.
<script type="text/javascript" language="javascript">
window.onload = CheckCountry;
function CheckCountry() {
var country = 'X';
var txtPhoneNumber = $('#txtPhoneNumber');
var maxLength = txtPhoneNumber.attr('maxLength');
var phoneNumber = txtPhoneNumber.val();
if (country == 'X') {
maxLength = '14';
phoneNumber = '963-';
txtPhoneNumber.on('keydown', function (e) {
return HandlePhoneNumberX(e, maxLength, phoneNumber);
});
} else {
maxLength = '12';
phoneNumber = '961-';
txtPhoneNumber.on('keydown', function (e) {
return HandlePhoneNumberY(e, maxLength, phoneNumber);
});
}
}
function HandlePhoneNumberX(e, maxLength, phoneNumber) { alert(maxLength + "-" + phoneNumber); }
function HandlePhoneNumberY(e, maxLength, phoneNumber) { alert(maxLength + "-" + phoneNumber); }
</script>
<asp:TextBox ID="txtPhoneNumber" onCopy="return false" onDrag="return false" onDrop="return false" onPaste="return false" clientidmode="Static" Font-Size="13px" Height="15px" runat="server" Width="105px" ></asp:TextBox>
</asp:Content>
Also, 2 validations function might not be needed. Just merge them into 1. I have not used the onkeydown attribute in the textbox declaration.