无法启动Rails服务器 - 无法找到JavaScript运行时

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$

即使我这样做也没用:

$ gem install execjs

我的Gemfile包含这个:

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]

Answer 1

您需要安装Javascript运行时,例如Node.js:

$ sudo apt-get install nodejs

Answer 2

您需要一个Javascript运行时.Execjs实际上是您可以使用的各种运行时的包装器.您仍然需要安装其中一个.几个系统已经带来一个可用的系统(MacOS和Windows).在其他人,你需要安装一个.

在错误描述中,它指向https://github.com/sstephenson/execjs#readme,它描述了几个支持的运行时(提示:始终读取错误消息!).在你的Gemfile,你会注意到有therubyracer引用的宝石(但注释掉了).它是受支持的运行时之一.

因此,你可以取消注释这个gem,运行bundle install并设置.