Javascript validation to allow only alpahbet or numeric value in textbox

Codes

charCode > 31 --> allow backspace to work

charCode > 32 --> allow space to work

 charCode <  97 || charCode >122 --> allow only alphabetic value

 charCode <  45 || charCode > 45 --> allow only - as special character

 charCode <  65 || charCode > 93 --> allow capslock character

 charCode <  65 || charCode > 90 --> allow only . as special character

 charCode <  48 || charCode > 57 --> allow numeric

/*For alpha and numeric*/

 <script type="text/javascript">
        function functionN1(evt) {
            if (evt.charCode > 32 && (evt.charCode < 48 || evt.charCode > 57) && (evt.charCode < 97 || evt.charCode > 122) && (evt.charCode < 65 || evt.charCode > 93)) {
                return false;
            }
        }
    </script>

 <asp:TextBox ID="txtcname" runat="server" onkeypress="return functionc(event)></asp:TextBox>

/*For numeric*/ 

 <script type="text/javascript">
        function functionx(evt) {
            if (evt.charCode > 31 && (evt.charCode < 48 || evt.charCode > 57)) {
                return false;
            }
        }
    </script>

 <asp:TextBox ID="txtcname" runat="server" onkeypress="return functionx(event)></asp:TextBox>

/*for alphabets*/

function functionN1(evt) {
            if (evt.charCode > 32 && (evt.charCode < 97 || evt.charCode > 122) && (evt.charCode < 65 || evt.charCode > 93)) {
                return false;
            }
        }
    </script>

 <asp:TextBox ID="txtcname" runat="server" onkeypress="return functionc(event)></asp:TextBox>