Rails 3 Could not find a JavaScript runtime. See https://github.com/sstephenson/execjs for a list of available runtimes.

Issue:
Could not find a JavaScript runtime. See https://github.com/sstephenson/execjs for a list of available runtimes.
/home/user/.rvm/gems/ruby-1.9.2-head/gems/execjs-1.2.6/lib/execjs/runtimes.rb:46:in `autodetect'
/home/user/.rvm/gems/ruby-1.9.2-head/gems/execjs-1.2.6/lib/execjs.rb:5:in `'
/home/user/.rvm/gems/ruby-1.9.2-head/gems/execjs-1.2.6/lib/execjs.rb:4:in `'
/home/user/.rvm/gems/ruby-1.9.2-head/gems/coffee-script-2.2.0/lib/coffee_script.rb:1:in `require'

Fix:

Add gem ‘therubyracer’ into Gemfile and then do a 'bundle install'