JS如何获取DataList中下拉菜单的值

[fuss228]

<div class="flf lb_r_goods_sy">
<div class="flf lb_r_goods_sy_l">
<div class="flf lb_r_goods_sy_size">
<label>
尺码选择：</label>
<asp:DropDownList ID="ddlColor" runat="server" DataTextField="Color" DataSource="<%#BindDetailProductColor(Container.DataItem.ToString()) %>"
DataValueField="ColorNumber" onChange="ChangeColor(this)">
</asp:DropDownList>
</div>
<div class="flf lb_r_goods_sy_color">
<label>
颜色选择：</label>
<asp:DropDownList ID="ddlSize" runat="server" DataTextField="SizeName" DataValueField="SizeNumber"
onChange="ChangeSize(this)">
<asp:ListItem Value="请选择">请选择</asp:ListItem>
</asp:DropDownList>
</div>
</div>
<div class="flf lb_r_goods_sy_r">
<a>
<asp:Image ID="ImageAdd" runat="server" ImageUrl="images/jrlb-btn.gif" Width="55px"
Height="55" onclick="AddLiBao(this)" />
</a>
</div>
</div>





点击图片 如何获取 上面2个DIV中 下拉菜单的ID 由于Datalist编译后服务器控件会变成DataList1_ctl00_ddlColor这样的ID
JS应该如何获取
JS代码:
function AddLiBao(obj) {

var num = obj.id.substr(13, 2);
var spanid = "DataList1_ctl" + num + "_lblProductNumber";
var Colorid = "DataList1_ctl" + num + "_ddlColor";
var Sizeid = "DataList1_ctl" + num + "_ddlSize";

虽然这样的办法比较笨 但还是能获取到的