allow only numbers in textbox jquery on keypress

function isNumberKey(evt) {
            var charCode = (evt.which) ? evt.which : event.keyCode
            if (charCode > 31 && (charCode < 48 || charCode > 57))
                return false;
            return true;
        }



<asp:TextBox ID="txtPinCode" runat="server" ClientIDMode="Static"
 onkeypress="return isNumberKey(event)"  MaxLength="13" />