Rails - May 2006 - Expanding javascript before sending it

Hi,

I had a simple javascript function directly in the rhtml with a rails
helper in it.
Before the page was sent to the client the rails help was of course expanded.

Moving it into a separated .js file, the rails code is, once again of
course,  no more expanded.

function save(id) {
   var el = document.getElementById(''s''+id);
   el.src = "<%=
theme_image_path(''loading.gif'')%>"
   new Ajax.Request(''/task/save/''+id, {asynchronous:true,
evalScripts:true,
onComplete:function(request){eval(request.responseText)},
parameters:Form.serialize(''tr''+id)});
   return false;
   }

<%= theme_image_path(''loading.gif'')%> is not more
expanded into pure
html once it is in a .js file.

Is there a way to generate the code before sending the js file to the client ?
Or is there another way of doing rails code into js ?

Thanks for your help,
Mickael.