Ruby on Rails

Hi Group,
I'm trying to see how Rails at ``startup time'' creates  Javascripts within the Clientside of the browser.

     rails s #starting my program

I've used both Byebug within Ruby code and Firefoxe's debugger within the browser.
==> Firefox's debug shows me the generated scripts like jquery etc but this is after the fact: the code producing the scripts has already executed.
       I want to observe how/when it generates the script and how various callbacks are registered particularly in jquery. Eg plot function using flot.

==> Byebug stops when the Ruby code does an eval expression when tracing from config/application.rb :
I used byebug's  set linetrace to observe the following:
Tracing: /Library/Ruby/Gems/2.0.0/gems/rack-1.6.4/lib/rack/builder.rb:33       options = {}
Tracing: /Library/Ruby/Gems/2.0.0/gems/rack-1.6.4/lib/rack/builder.rb:34       if config =~ /\.ru$/
Tracing: /Library/Ruby/Gems/2.0.0/gems/rack-1.6.4/lib/rack/builder.rb:35         cfgfile = ::File.read(config)
Tracing: /Library/Ruby/Gems/2.0.0/gems/rack-1.6.4/lib/rack/builder.rb:36         if cfgfile[/^#\\(.*)/] && opts
Tracing: /Library/Ruby/Gems/2.0.0/gems/rack-1.6.4/lib/rack/builder.rb:39         cfgfile.sub!(/^__END__\n.*\Z/m, '')
Tracing: /Library/Ruby/Gems/2.0.0/gems/rack-1.6.4/lib/rack/builder.rb:40         app = new_from_string cfgfile, config
Tracing: /Library/Ruby/Gems/2.0.0/gems/rack-1.6.4/lib/rack/builder.rb:49       eval "Rack::Builder.new {\n" + builder_script + "\n}.to_app",
Tracing: /Library/Ruby/Gems/2.0.0/gems/rack-1.6.4/lib/rack/builder.rb:49       eval "Rack::Builder.new {\n" + builder_script + "\n}.to_app",

where the eval statement just sits and waits. At that point I had to abort the program at startup using Cntl C

My questions so far are:
   1) how to trace  outside programs  called by Ruby like Rack::Builder'' above to continue my investigations. Other more powerfull debug tracers to use? DTRACE?
      1.5) Can break points be placed against the source code before the dynamic tracing begins? or have a pre-programmed script set the breakpoints at runtime?

   2) how is javascript executed by ``Ruby start up''  to manufacture the local registered scripts: ie, the various crossovers between Ruby and Javascript contexts

Any pointers to documents/websites/forums where these questions allow me to continue my investigations is appreciated

I thank you in advance for your ``eyes and ears'' evaluating my request
Dave