"Expected expression" with <%=foo%> inside JavaScript in .aspx file

Question

I've got code like this in an .aspx file:

<script type="text/javascript" language="javascript">
function init()
{
     <%= x %>
}

It works fine (x is a string that will be bound to some JavaScript at runtime), but when compiling I get an "Expected expression" warning on the <%=

I know it's not the nicest code in the world, but there are various historical bits of code that like to inject little bits of JavaScript into the page. All perfectly innocent :)

Answer 1

The warning is happening because the code block is inside a JavaScript <script> block; the compiler is trying to be smart about recognizing the difference between HTML/controls and JavaScript.

Although it's a bit ugly, you should be able to eliminate the warning by using eval('<%= x %>')

You might also have a look at an article I wrote on using ASP.NET to create dynamic JavaScript: http://www.12titans.net/p/dynamic-javascript.aspx

Answer 2

If you wanted to be perfectly legal, use a literal:

<asp:Literal ID="litX" runat="server"></asp:Literal>

and set its Text to the whole <script type="text/javascript" language="javascript">...</script> block on the server side.