将DropDownList值保存到javascript变量中

Question

I am relatively new to C#, and I have been researching this across the internet for a few days now. I need the value selected in asp.net DropDownList to be declared as a JavaScript variable. I have looked into <asp:hiddenfield> 's mostly, but I'm not sure if this is the best option to go down. So I have two questions:

1. Are <asp:hiddenfield> 's the best option?

2. How do you declare a C# string into a javascript variable?

    <asp:DropDownList runat="server" ID="dropDownID"> <asp:ListItem Text="-- Select Reason --" Value=""></asp:ListItem> <asp:ListItem Text="Booking" Value="1"></asp:ListItem> <asp:ListItem Text="Discussing" Value="2"></asp:ListItem> <asp:ListItem Text="Quotation" Value="3"></asp:ListItem> </asp:DropDownList> <asp:hiddenfield ID="valueInHiddenField" value="" runat="server"/> 

Answer 1

<script type="text/javascript">
    var serverDropdown = document.getElementById('dropDownID');
    var reasonIndex = serverDropdown.selectedIndex;
    var reasonValue = serverDropdown.value;
</script>

Answer 2

Change this <asp:DropDownList runat="server" ID="dropDownID"> to this:

<asp:DropDownList runat="server" ID="dropDownID" ClientIDMode="Static">

and then use this JavaScript to get the value:

var val = document.getElementById('dropDownID').value;

Answer 3

To store dropdownlist value in javascript variable, there is no need to use hidden field,

try this...

 <script type="text/javascript">
     var dropdown_value = document.getElementById('<%=dropDownID.ClientID%>').value;
 </script>

here instead of dropdownID we have to use its ClientID.....In asp.net 4.0 you can direclty use its id by doing ClientIDMode="Static" of the dropdown.

     var dropdown_value = document.getElementById('dropDownID').value;