无法启动Rails服务器 – 无法findJavaScript运行时
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$ 甚至我没有这样做：
$ 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]
你需要一个Javascript运行时。 Execjs实际上是你可以使用的各种运行时的包装。 你仍然需要安装其中的一个。 几个系统已经带来了一个可用的（MacOS和Windows）。 在别人身上，你需要安装一个。
在错误描述中，它指向了https://github.com/sstephenson/execjs#readme ，它描述了几个支持的运行时（提示：总是读取错误信息！）。 在您的Gemfile ，您会注意到引用了therubyracer gem（但已注释掉）。 这是受支持的运行时间之一。
因此，你可以取消注释这个gem，运行bundle install和设置。
您需要安装一个Javascript运行时，例如Node.js ：
$ sudo apt-get install nodejs