javascript runtime in rails 3.1.0 and ruby 1.9.2. cant deal with with heroku. Did everything, but still does not working

Question

Please help, it's my studying project. It work locally but not online:
Hello, it is said that i dont need special gems like "therubyracer" in rails 3.1.0 but it writes in "heroku logs":

    2011-10-04T23:15:30+00:00 app[web.1]: ActionView::Template::Error (Could not fin
d a JavaScript runtime. See https://github.com/sstephenson/execjs for a list of
available runtimes.
2011-10-04T23:15:30+00:00 app[web.1]:   (in /app/app/assets/javascripts/rails.js
)):....

i was trying to install "therubyracer" but i have error with installing it

C:\proj\lagp>gem install therubyracer
Temporarily enhancing PATH to include DevKit...
Building native extensions.  This could take a while...
ERROR:  Error installing therubyracer:
        ERROR: Failed to build gem native extension.

        C:/RailsInstaller/Ruby1.9.2/bin/ruby.exe extconf.rb
checking for main() in -lpthread... no
creating Makefile

make
C:/RailsInstaller/Ruby1.9.2/bin/ruby -e "puts 'EXPORTS', 'Init_v8'"  > v8-i386-m
ingw32.def
g++ -I. -IC:/RailsInstaller/Ruby1.9.2/lib/ruby/gems/1.9.1/gems/libv8-3.3.10.2/li
b/libv8/v8/include -IC:/RailsInstaller/Ruby1.9.2/include/ruby-1.9.1/i386-mingw32.....

also i made compile:true and precompiled

Here is my app in a github: https://github.com/EnotPoloskun/lagp
take a look plz if you have a time, i wasted 2 days for this problem(
so i dont know what to do(,
Thanks in advance

Answer 1

I'm using Rails 3.1 on Heroku with the assets pipeline, in addition to the assets group in my gemfile I have;

group :production do
 gem 'therubyracer-heroku'
end

which seems to be what you're missing,

Answer 2

group :production do

gem 'therubyracer-heroku'

end

Then bundle update at local machine before uploading source code to heroku.