asp.net的js中获取控件的ClientID

<tr>
                        <td width="110" height="35" align="center" style="font-weight: bolder">
                            出生年月
                        </td>
                        <td style="font-size: 14px">
                            <asp:TextBox ID="txtBirth" ReadOnly="true" runat="server"></asp:TextBox>
                        </td>
                        <td width="110" height="28" align="center" style="font-weight: bolder">
                            性别
                        </td>
                        <td style="font-size: 14px">
                            <asp:TextBox ReadOnly="true" ID="txtSex" runat="server"></asp:TextBox>
                        </td>
                    </tr>

这是很普通的两个控件，但是我们一旦结合母版页，控件ID中就会出现一下母版页特有的表示，js货jQuery获取不便。那么怎么办呢？

<script language="javascript">
        $(function () {
            var sexId = "<%=txtSex.ClientID %>";