Only Text Field Validations Using Javascript

<table align="center">
    <tr>
    <td>
    Employee Name
    </td>
    <td>
    <asp:TextBox ID="txtName" Onchange="return ValidateName(this)"  runat="server"></asp:TextBox>
    </td>
    </tr>
</table>

<script type="text/javascript" language="javascript"> 
function ValidateName(x) {
            var AlphExp = /^[a-zA-Z]+$/;
            if (x.value.match(AlphExp))
            {
                return true;                   
            }
            else
            {
                alert("Invalid Name");
                x.value = "";
                x.focus();
                return false;    
            }
        }
</script>