Can't start Rails Server - Could not find a JavaScript runtime

Question

pallav@pallav-System-Product-Name:~/Workspace/blog$ rails server

/home/pallav/.rvm/gems/ruby-2.0.0-p353/gems/execjs-2.0.2/lib/execjs/runtimes.rb:51:in `autodetect': Could not find a JavaScript runtime. See https://github.com/sstephenson/execjs for a list of available runtimes. (ExecJS::RuntimeUnavailable)
  from /home/pallav/.rvm/gems/ruby-2.0.0-p353/gems/execjs-2.0.2/lib/execjs.rb:5:in `<module:ExecJS>'
  from /home/pallav/.rvm/gems/ruby-2.0.0-p353/gems/execjs-2.0.2/lib/execjs.rb:4:in `<top (required)>'
  from /home/pallav/.rvm/gems/ruby-2.0.0-p353/gems/uglifier-2.4.0/lib/uglifier.rb:3:in `require'
  from /home/pallav/.rvm/gems/ruby-2.0.0-p353/gems/uglifier-2.4.0/lib/uglifier.rb:3:in `<top (required)>'
  from /home/pallav/.rvm/gems/ruby-2.0.0-p353/gems/bundler-1.5.2/lib/bundler/runtime.rb:76:in `require'
  from /home/pallav/.rvm/gems/ruby-2.0.0-p353/gems/bundler-1.5.2/lib/bundler/runtime.rb:76:in `block (2 levels) in require'
  from /home/pallav/.rvm/gems/ruby-2.0.0-p353/gems/bundler-1.5.2/lib/bundler/runtime.rb:72:in `each'
  from /home/pallav/.rvm/gems/ruby-2.0.0-p353/gems/bundler-1.5.2/lib/bundler/runtime.rb:72:in `block in require'
  from /home/pallav/.rvm/gems/ruby-2.0.0-p353/gems/bundler-1.5.2/lib/bundler/runtime.rb:61:in `each'
  from /home/pallav/.rvm/gems/ruby-2.0.0-p353/gems/bundler-1.5.2/lib/bundler/runtime.rb:61:in `require'
  from /home/pallav/.rvm/gems/ruby-2.0.0-p353/gems/bundler-1.5.2/lib/bundler.rb:131:in `require'
  from /home/pallav/Workspace/blog/config/application.rb:7:in `<top (required)>'
  from /home/pallav/.rvm/gems/ruby-2.0.0-p353/gems/railties-4.0.2/lib/rails/commands.rb:74:in `require'
  from /home/pallav/.rvm/gems/ruby-2.0.0-p353/gems/railties-4.0.2/lib/rails/commands.rb:74:in `block in <top (required)>'
  from /home/pallav/.rvm/gems/ruby-2.0.0-p353/gems/railties-4.0.2/lib/rails/commands.rb:71:in `tap'
  from /home/pallav/.rvm/gems/ruby-2.0.0-p353/gems/railties-4.0.2/lib/rails/commands.rb:71:in `<top (required)>'
  from bin/rails:4:in `require'
  from bin/rails:4:in `<main>'

pallav@pallav-System-Product-Name:~/Workspace/blog$

It didn't worked even i did this:

$ gem install execjs

My Gemfile contains this:

source 'https://rubygems.org'

# Bundle edge Rails instead: gem 'rails', github: 'rails/rails'
gem 'rails', '4.0.2'

# Use sqlite3 as the database for Active Record
gem 'sqlite3'

# Use SCSS for stylesheets
gem 'sass-rails', '~> 4.0.0'

# 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', '~> 1.2'

group :doc do
  # bundle exec rake doc:rails generates the API under doc/api.
  gem 'sdoc', require: false
end

# Use ActiveModel has_secure_password
# gem 'bcrypt-ruby', '~> 3.1.2'

# Use unicorn as the app server
# gem 'unicorn'

# Use Capistrano for deployment
# gem 'capistrano', group: :development

# Use debugger
# gem 'debugger', group: [:development, :test]

If you're on a modern macOS, try upgrading execjs gem to 2.8.0+. — Joshua Pinter
– Joshua Pinter, Commented Jun 30, 2021 at 16:17

Agis · Accepted Answer · 2014-01-16 14:27:00Z

16

You need a Javascript runtime installed, like Node.js for example:

$ sudo apt-get install nodejs

edited Jan 16, 2014 at 14:27

answered Jan 16, 2014 at 13:54

Agis

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2 Comments

PallavSharma Over a year ago

Description: Ubuntu 13.10 x86_64

Wayne Conrad Over a year ago

For Ubuntu and Debian, use apt-get instead of brew

Holger Just · Accepted Answer · 2014-01-16 14:19:22Z

8

You need a Javascript runtime. Execjs is in fact a wrapper around various runtimes you could use. You still need to install one of them. Several systems already bring a usable one (MacOS and Windows). On others, you need to install one.

In the error description, it pointed you towards https://github.com/sstephenson/execjs#readme which describes several of the supported runtimes (Hint: Always read error messages!). In your Gemfile, you'll notice that there is the therubyracer gem referenced (but commented out). It is one of the supported runtimes.

Thus, you could just uncomment this gem, run bundle install and be set.

answered Jan 16, 2014 at 14:19

Holger Just

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