[The js foreground obtains the value of the server control RadComboBox]

The js foreground gets the selected item (text and value) of the server control RadComboBox

server control

<telerik:RadComboBox ID="ddlMine" AutoPostBack="true" Enabled="true" 
        CheckedItemsTexts="DisplayAllInInput" DropDownAutoWidth="Disabled" MaxHeight="300"
        runat="server"  EnableCheckAllItemsCheckBox="true" Width="150px">
</telerik:RadComboBox>

js get selected item

var combobox = $find("<%= ddlMine.ClientID %>");
            var mName = combobox.get_selectedItem().get_text();
            var mCode = combobox.get_selectedItem().get_value();