How to find the selected element in a list in javascript

I have a jsp that I'm working on and I need to find out which item in a list is selected.

here is a screen shot of the jsp:

here is the code:

<% Venue v = (Venue)session.getAttribute("currentVenue"); %>
<% List<Conceptual_Package> cpList = Conceptual_PackageDAO.getInstance().getByVenue(v.getId()); %>

What Packages do you want to see?

 <form开发者_如何学运维 method="post" action="ttp.actions.Sale3PackAction.action">
 <select name="packid" id="packid">
     <% for (Conceptual_Package cp: cpList) { %>
    <option value="<%=cp.getId()%>"><%=cp.getName1()%></option>
    <% } %>


 </select>

    <input type="button" value="  next  " onclick="getSeats();"/>

    </form>


<!--new-->


Available Seats:

 <select name="aSeats" size="10" id="aSeats">

 </select>


    <input type="button" value="  add  " onclick="addToCart();"/>


Selected Seats:
 <form method="post" action="ttp.actions.sale4Action.action">
     <select name="Seat2" size="10" id="seat2">

     </select>



    </form>



<jsp:include page="/footer.jsp"/>

You can get the selected <option> DOM object by talking to the <select> object:

var select = document.getElementById('packId');
var selectedOption = select.options[select.selectedIndex];
alert("Selected option: " + selectedOption.value);

You can find out the index of the selected option with the selectedIndex property.

var index = document.getElementById('packid').selectedIndex;

If it is the value attribute you want, you can use this (assuming index from above)...

var value = document
             .getElementById('packid')
             .getElementsByTagName('option')[index]
             .value;

It is best to cache a pointer to the select element however so you don't need to select it twice :)