Rake aborted, Error while trying to load the gem 'uglifier'

Question

I'm following 'Getting Started with Ruby on Heroku', but when attempting to run the demo app locally with

$ bundle exec rake db:create db:migrate 

I get

sam@samoliver:~/ruby-getting-started$ bundle exec rake db:create db:migrate --trace rake aborted! Bundler::GemRequireError: There was an error while trying to load the gem 'uglifier'. /home/sam/.rvm/gems/ruby-2.2.3/gems/bundler-1.11.0/lib/bundler/runtime.rb:80:in `rescue in block (2 levels) in require' /home/sam/.rvm/gems/ruby-2.2.3/gems/bundler-1.11.0/lib/bundler/runtime.rb:76:in `block (2 levels) in require' /home/sam/.rvm/gems/ruby-2.2.3/gems/bundler-1.11.0/lib/bundler/runtime.rb:72:in `each' /home/sam/.rvm/gems/ruby-2.2.3/gems/bundler-1.11.0/lib/bundler/runtime.rb:72:in `block in require' /home/sam/.rvm/gems/ruby-2.2.3/gems/bundler-1.11.0/lib/bundler/runtime.rb:61:in `each' /home/sam/.rvm/gems/ruby-2.2.3/gems/bundler-1.11.0/lib/bundler/runtime.rb:61:in `require' /home/sam/.rvm/gems/ruby-2.2.3/gems/bundler-1.11.0/lib/bundler.rb:99:in `require' /home/sam/ruby-getting-started/config/application.rb:7:in `<top (required)>' /home/sam/ruby-getting-started/Rakefile:4:in `require' /home/sam/ruby-getting-started/Rakefile:4:in `<top (required)>' /home/sam/.rvm/rubies/ruby-2.2.3/lib/ruby/2.2.0/rake/rake_module.rb:28:in `load' /home/sam/.rvm/rubies/ruby-2.2.3/lib/ruby/2.2.0/rake/rake_module.rb:28:in `load_rakefile' /home/sam/.rvm/rubies/ruby-2.2.3/lib/ruby/2.2.0/rake/application.rb:689:in `raw_load_rakefile' /home/sam/.rvm/rubies/ruby-2.2.3/lib/ruby/2.2.0/rake/application.rb:94:in `block in load_rakefile' /home/sam/.rvm/rubies/ruby-2.2.3/lib/ruby/2.2.0/rake/application.rb:176:in `standard_exception_handling' /home/sam/.rvm/rubies/ruby-2.2.3/lib/ruby/2.2.0/rake/application.rb:93:in `load_rakefile' /home/sam/.rvm/rubies/ruby-2.2.3/lib/ruby/2.2.0/rake/application.rb:77:in `block in run' /home/sam/.rvm/rubies/ruby-2.2.3/lib/ruby/2.2.0/rake/application.rb:176:in `standard_exception_handling' /home/sam/.rvm/rubies/ruby-2.2.3/lib/ruby/2.2.0/rake/application.rb:75:in `run' /home/sam/.rvm/rubies/ruby-2.2.3/bin/rake:33:in `<main>' ExecJS::RuntimeUnavailable: Could not find a JavaScript runtime. See https://github.com/sstephenson/execjs for a list of available runtimes. /home/sam/.rvm/gems/ruby-2.2.3/gems/execjs-2.2.2/lib/execjs/runtimes.rb:51:in `autodetect' /home/sam/.rvm/gems/ruby-2.2.3/gems/execjs-2.2.2/lib/execjs.rb:5:in `<module:ExecJS>' /home/sam/.rvm/gems/ruby-2.2.3/gems/execjs-2.2.2/lib/execjs.rb:4:in `<top (required)>' /home/sam/.rvm/gems/ruby-2.2.3/gems/uglifier-2.5.3/lib/uglifier.rb:3:in `require' /home/sam/.rvm/gems/ruby-2.2.3/gems/uglifier-2.5.3/lib/uglifier.rb:3:in `<top (required)>' /home/sam/.rvm/gems/ruby-2.2.3/gems/bundler-1.11.0/lib/bundler/runtime.rb:77:in `require' /home/sam/.rvm/gems/ruby-2.2.3/gems/bundler-1.11.0/lib/bundler/runtime.rb:77:in `block (2 levels) in require' /home/sam/.rvm/gems/ruby-2.2.3/gems/bundler-1.11.0/lib/bundler/runtime.rb:72:in `each' /home/sam/.rvm/gems/ruby-2.2.3/gems/bundler-1.11.0/lib/bundler/runtime.rb:72:in `block in require' /home/sam/.rvm/gems/ruby-2.2.3/gems/bundler-1.11.0/lib/bundler/runtime.rb:61:in `each' /home/sam/.rvm/gems/ruby-2.2.3/gems/bundler-1.11.0/lib/bundler/runtime.rb:61:in `require' /home/sam/.rvm/gems/ruby-2.2.3/gems/bundler-1.11.0/lib/bundler.rb:99:in `require' /home/sam/ruby-getting-started/config/application.rb:7:in `<top (required)>' /home/sam/ruby-getting-started/Rakefile:4:in `require' /home/sam/ruby-getting-started/Rakefile:4:in `<top (required)>' /home/sam/.rvm/rubies/ruby-2.2.3/lib/ruby/2.2.0/rake/rake_module.rb:28:in `load' /home/sam/.rvm/rubies/ruby-2.2.3/lib/ruby/2.2.0/rake/rake_module.rb:28:in `load_rakefile' /home/sam/.rvm/rubies/ruby-2.2.3/lib/ruby/2.2.0/rake/application.rb:689:in `raw_load_rakefile' /home/sam/.rvm/rubies/ruby-2.2.3/lib/ruby/2.2.0/rake/application.rb:94:in `block in load_rakefile' /home/sam/.rvm/rubies/ruby-2.2.3/lib/ruby/2.2.0/rake/application.rb:176:in `standard_exception_handling' /home/sam/.rvm/rubies/ruby-2.2.3/lib/ruby/2.2.0/rake/application.rb:93:in `load_rakefile' /home/sam/.rvm/rubies/ruby-2.2.3/lib/ruby/2.2.0/rake/application.rb:77:in `block in run' /home/sam/.rvm/rubies/ruby-2.2.3/lib/ruby/2.2.0/rake/application.rb:176:in `standard_exception_handling' /home/sam/.rvm/rubies/ruby-2.2.3/lib/ruby/2.2.0/rake/application.rb:75:in `run' /home/sam/.rvm/rubies/ruby-2.2.3/bin/rake:33:in `<main>' sam@samoliver:~/ruby-getting-started$  

I tried removing and adding 'uglifier' (2.5.3) again to no effect and I do have 'therubyracer' installed, so I don't understand what is ExecJS complaining about.

Gemfile

source 'https://rubygems.org' ruby '2.2.3'  # Bundle edge Rails instead: gem 'rails', github: 'rails/rails' gem 'rails', '4.2.3' # Use postgresql as the database for Active Record gem 'pg' gem 'rails_12factor', group: :production # Use SCSS for stylesheets gem 'sass-rails', '~> 5.0.3' # Use Uglifier as compressor for JavaScript assets gem 'uglifier', '>= 1.3.0' # Use CoffeeScript for .js.coffee assets and views gem 'coffee-rails', '~> 4.0.0' # See https://github.com/sstephenson/execjs#readme for more supported runtimes # gem 'therubyracer',  platforms: :ruby  # Use jquery as the JavaScript library gem 'jquery-rails' # Turbolinks makes following links in your web application faster. Read more: https://github.com/rails/turbolinks gem 'turbolinks' # Build JSON APIs with ease. Read more: https://github.com/rails/jbuilder gem 'jbuilder', '~> 2.0' # bundle exec rake doc:rails generates the API under doc/api. gem 'sdoc', '~> 0.4.0',          group: :doc  # Spring speeds up development by keeping your application running in the background. Read more: https://github.com/rails/spring gem 'spring',        group: :development  # Use ActiveModel has_secure_password # gem 'bcrypt', '~> 3.1.7'  gem 'puma'  # Use Capistrano for deployment # gem 'capistrano-rails', group: :development  # Use debugger # gem 'debugger', group: [:development, :test] 

Answer 1

install nodejs

apt-get install nodejs