求助~~~~~~~~~~~~~

Question

<ext:ComboBox ID="CB_Language" runat="server" FieldLabel="语言" Width="120" EmptyText="请选择" AllowBlank="false">  <Items>  <ext:ListItem Value="A" Text="英语" />  <ext:ListItem Value="B" Text="汉语" />  </Items>     </ext:ComboBox>我想得到选择项的value，var u=document.getElementById("CB_LanguageTest");  u.value得到的是Text，怎么得到value？