This is a real problem if you have javascript files for your Facebook application and wish to keep your code DRY. Here is the solution I came up with using Ruby on Rails and Facebooker :

# ApplicationController.rb
helper_method :request_is_facebook_tab? # Make the facebooker method available in views and helpers

# Application.fbml.erb
<%= render :partial => 'facebook/fb_js' %>

# _fb_js.fbml.erb
<% if request_is_facebook_tab? %>
  <%= javascript_tag output_js_files_content("Utility.js", "FBjqRY.min.js", "application-fb.js") %>
<% else %>
  <%= javascript_include_tag "Utility.js", "FBjqRY.min.js", "application-fb.js" %>
<% end %>

# facebook_helper.rb
def output_js_files_content(*files)
    output = files.collect { |f| IO.read(File.join(RAILS_ROOT, 'public', 'javascripts', f)) }
    output.join("\n")
end

This code will detect wether or not the facebook application is running inside a profile tab. If so, instead of generating an external javascript tag, an helper method is called to dump all the content of javascript files inside a script tag.

This solution lets keep your javascript where it belongs (inside .js files) and keep your code DRY when dealing with profile tabs limitation.

// Alternates the background colors of the elements passed in parameters
// elems  - Array of jQuery DOM objects
// colors - Array of hexadecimal colors
function alternateBgColor(elems, colors) {
  elems.each( function(index){
    var colorIndex = index % colors.length;
    $(this).css('background-color', colors[colorIndex]);
  });
}

It’s only a three lines function but the cool thing about it is that you can alternate through as many colors as you need. I’m only using two for now but this could come useful at some point! I like how everything javascript just got easier with jQuery.