How to Populate asp:Textbox using value in ComboBox

Question

I have this combobox and I need to populate a textbox with the selected combobox value on the clientside. What I have doesn't seem to be working. Am I doing this correctly?

<asp:ComboBox ID="cmbOutputRating" runat="server" 
DropDownStyle="DropDown" 
AutoCompleteMode="Suggest" 
CaseSensitive="false" 
RenderMode="Inline" 
ItemInsertLocation="Append"
onchange="javascript:ddlChange();">
</asp:ComboBox>

Here is the textbox:

<asp:TextBox ID="txtOutputRating" runat="server" 
CssClass="inputFieldSmall" 
OnTextChanged="txtOutputRating_TextChanged"
AutoPostBack="True" 
meta:resourcekey="txtOutputRatingResource1">
</asp:TextBox>

Here is the javascript:

<asp:Content ID="Content1" ContentPlaceHolderID="HeadContent" runat="server">
<script type="text/javascript">
function ddlChange() 
{
    var cmb = document.getElementById('<%=cmbOutputRating.ClientID %>');
    var textBox = document.getElementById('<%= txtOutputRating.ClientID%>');
    textBox.value = cmb.options[cmb.selectedIndex].value;
}
</script>
</asp:Content>

Answer 1

The combobox is rendered as an input so you would grab the value of it like so:

<script type="text/javascript">
function ddlChange() 
{
var cmb = document.getElementById('<%=cmbOutputRating.ClientID %>');
var textBox = document.getElementById('<%= txtOutputRating.ClientID%>');
textBox.value = cmb.value;
}
</script>