java script email validation

<script type="text/javascript">
        function checkEmail() {
            if (document.getElementById("<%=txtname.ClientID%>").value == "") {
                alert("Current Password Field is Required !")
                document.getElementById("<%=txtname.ClientID%>").focus();
                return false;
            }
            if(name.value==0){
                aler('enter name');
                return false;
            }

            var email = document.getElementById('txtemail');
            var filter = /^([a-zA-Z0-9_\.\-])+\@(([a-zA-Z0-9\-])+\.)+([a-zA-Z0-9]{2,4})+$/;

            if (!filter.test(email.value)) {
                alert('Please provide a valid email address');
                email.focus;
                return false;
            }

        }
    </script>

<asp:Button ID="btnsubmit" Text="save" runat="server" OnClientClick="return checkEmail() " />