怎样用JS为dorpdownlist赋默认值

Question

<asp:DropDownList style="float:left;" ID="DDL_ShowCompanyName" runat="server" OnSelectedIndexChanged="DDL_NewsTName_SelectedIndexChanged"
            AutoPostBack="True">
        </asp:DropDownList>
<asp:DropDownList ID="DDL_CompanyName" runat="server" Width="155px">
                                </asp:DropDownList>
用JS把第一个的选中值赋给第二个当作默认值
请帮忙

Answer 1

s1 = document.getElementById('<%=DDL_ShowCompanyName.ClientID%>')
s2 = document.getElementById('<%=DDL_CompanyName.ClientID%>')for(i=0;i<s2.options.length;i++)
{
 if(s2.options[i].value==s1.value) s2.options[i].selected=true
}