Client Side Validation in asp.net, Required Field,MobileNo,Blank Field

<script language="javascript" type="text/javascript">
    function validate() {
        if (document.getElementById("<%=txtFirstName.ClientID%>").value == "") {
            alert("Name Field can not be blank");
            document.getElementById("<%=txtFirstName.ClientID%>").focus();
            return false;
        }
        if (document.getElementById("<%=txtEmail.ClientID%>").value == "") {
            alert("Email Field can not be blank");
            document.getElementById("<%=txtEmail.ClientID%>").focus();
            return false;
        }
        if (document.getElementById("<%=txtPhone.ClientID%>").value == "") {
            alert(" Phone Field can not be blank");
            document.getElementById("<%=txtPhone.ClientID%>").focus();
            return false;
        }
        if (document.getElementById("<%=txtEmergencyContact.ClientID%>").value == "") {
            alert("Emergency Contact Field can not be blank");
            document.getElementById("<%=txtEmergencyContact.ClientID%>").focus();
            return false;
        }

        if (document.getElementById("<%=txtAge.ClientID%>").value == "") {
            alert("Age Field can not be blank");
            document.getElementById("<%=txtAge.ClientID%>").focus();
            return false;
        }
        if (document.getElementById("<%=txtPreferred.ClientID%>").value == "") {
            alert("Preferred Partner Field can not be blank");
            document.getElementById("<%=txtPreferred.ClientID%>").focus();
            return false;
        }

    
     
        if (document.getElementById("<%=txtPhone.ClientID%>").value == "") {
            alert("Mobile No is not valid");
            document.getElementById("<%=txtPhone.ClientID%>").focus();
            return false;
        }
        var digits = /^([0-9]{10})$/;
        var digitsid = document.getElementById("<%=txtPhone.ClientID %>").value;
        var digitsArray = digitsid.match(digits);
        var temp;
        if (digitsArray == null) {
            alert("Your mobile seems incorrect. Please try again.");
            document.getElementById("<%=txtPhone.ClientID %>").focus();
            return false;
        }
        var digits = /^([0-9]{10})$/;
        var digitsid = document.getElementById("<%=txtEmergencyContact.ClientID %>").value;
        var digitsArray = digitsid.match(digits);
        var temp;
        if (digitsArray == null) {
            alert("Your Emergency Contact seems incorrect. Please try again.");
            document.getElementById("<%=txtEmergencyContact.ClientID %>").focus();
            return false;
        }
       
        return true;
    }
</script>


In Submit Button We have

  <asp:Button CssClass="button" ID="btnNameEmail" runat="server" Text="Submit" OnClick="btnNameEmail_Click" OnClientClick ="return Validate(this)" />

Call the JavaScript Function