Rails (ExecJS::RuntimeUnavailable) 錯誤

當輸入rails server出現類似以下錯誤訊息時

roli@roli-virtual-machine ~/rails_projects/first_app $ rails server
/home/roli/.rvm/gems/ruby-1.9.3-p125/gems/execjs-1.3.0/lib/execjs/runtimes.rb:50:in `autodetect': Could not find a JavaScript runtime. See https://github.com/sstephenson/execjs for a list of available runtimes. (ExecJS::RuntimeUnavailable)
from /home/roli/.rvm/gems/ruby-1.9.3-p125/gems/execjs-1.3.0/lib/execjs.rb:5:in `'
from /home/roli/.rvm/gems/ruby-1.9.3-p125/gems/execjs-1.3.0/lib/execjs.rb:4:in `'
from /home/roli/.rvm/gems/ruby-1.9.3-p125/gems/coffee-script-2.2.0/lib/coffee_script.rb:1:in `require'
from /home/roli/.rvm/gems/ruby-1.9.3-p125/gems/coffee-script-2.2.0/lib/coffee_script.rb:1:in `'
from /home/roli/.rvm/gems/ruby-1.9.3-p125/gems/coffee-script-2.2.0/lib/coffee-script.rb:1:in `require'
from /home/roli/.rvm/gems/ruby-1.9.3-p125/gems/coffee-script-2.2.0/lib/coffee-script.rb:1:in `'
from /home/roli/.rvm/gems/ruby-1.9.3-p125/gems/coffee-rails-3.2.2/lib/coffee-rails.rb:1:in `require'
from /home/roli/.rvm/gems/ruby-1.9.3-p125/gems/coffee-rails-3.2.2/lib/coffee-rails.rb:1:in `'
from /home/roli/.rvm/gems/ruby-1.9.3-p125/gems/bundler-1.0.22/lib/bundler/runtime.rb:68:in `require'
from /home/roli/.rvm/gems/ruby-1.9.3-p125/gems/bundler-1.0.22/lib/bundler/runtime.rb:68:in `block (2 levels) in require'
from /home/roli/.rvm/gems/ruby-1.9.3-p125/gems/bundler-1.0.22/lib/bundler/runtime.rb:66:in `each'
from /home/roli/.rvm/gems/ruby-1.9.3-p125/gems/bundler-1.0.22/lib/bundler/runtime.rb:66:in `block in require'
from /home/roli/.rvm/gems/ruby-1.9.3-p125/gems/bundler-1.0.22/lib/bundler/runtime.rb:55:in `each'
from /home/roli/.rvm/gems/ruby-1.9.3-p125/gems/bundler-1.0.22/lib/bundler/runtime.rb:55:in `require'
from /home/roli/.rvm/gems/ruby-1.9.3-p125/gems/bundler-1.0.22/lib/bundler.rb:122:in `require'
from /home/roli/rails_projects/first_app/config/application.rb:7:in `'
from /home/roli/.rvm/gems/ruby-1.9.3-p125/gems/railties-3.2.1/lib/rails/commands.rb:53:in `require'
from /home/roli/.rvm/gems/ruby-1.9.3-p125/gems/railties-3.2.1/lib/rails/commands.rb:53:in `block in '
from /home/roli/.rvm/gems/ruby-1.9.3-p125/gems/railties-3.2.1/lib/rails/commands.rb:50:in `tap'
from /home/roli/.rvm/gems/ruby-1.9.3-p125/gems/railties-3.2.1/lib/rails/commands.rb:50:in `'
from script/rails:6:in `require'
from script/rails:6:in `

'

到你的application資料夾下修改Gemfile

加入下面兩行

gem 'execjs'
gem 'therubyracer'

然後進行bundle install即可成功rails server