Git Bash中启动Rails Server报错求助：缺少JavaScript运行时

嘿，我之前也踩过这个坑！别慌，咱们一步步来排查解决：

第一步：确认Node.js是否真的能被终端识别 #

你说已经装了Node.js，但有时候安装后终端（比如你用的Git Bash）没及时读取新的环境变量，导致Rails找不到它。先打开Git Bash输入：

node -v

如果能输出类似v18.17.0这样的版本号，说明Node是正常可用的；如果提示command not found，那你得把Node的安装路径加到系统的环境变量PATH里，然后重启Git Bash再试。

第二步：调整Gemfile并重新安装依赖 #

你取消了# gem 'therubyracer', platforms: :ruby的注释，但其实有Node.js的话，therubyracer完全没必要装——它是Ruby实现的JS运行时，和Node功能重复，反而可能导致冲突。建议你把这行重新注释掉，然后在项目根目录运行：

bundle install

确保依赖安装正确。

第三步：强制指定ExecJS使用Node.js #

如果上面两步都试过还是不行，咱们可以手动告诉ExecJS用Node作为运行时：
在你的Rails项目里创建config/initializers/execjs.rb文件，写入以下内容：

ExecJS.runtime = ExecJS::Runtimes::Node

保存后再运行rails s试试，应该就能正常启动了。

你的报错详情： #

$ rails s 
c:/RailsInstaller/Ruby2.3.3/lib/ruby/gems/2.3.0/gems/bundler-1.15.3/lib/bundler/runtime.rb:85:in `rescue in block (2 levels) in require': There was an error while trying to load the gem 'uglifier'. (Bundler::GemRequireError)
Gem Load Error is: Could not find a JavaScript runtime. See https://github.com/rails/execjs for a list of available runtimes.
Backtrace for gem load error is:
c:/RailsInstaller/Ruby2.3.3/lib/ruby/gems/2.3.0/gems/execjs-2.7.0/lib/execjs/runtimes.rb:58:in `autodetect'
c:/RailsInstaller/Ruby2.3.3/lib/ruby/gems/2.3.0/gems/execjs-2.7.0/lib/execjs.rb:5:in `<module:ExecJS>'
c:/RailsInstaller/Ruby2.3.3/lib/ruby/gems/2.3.0/gems/execjs-2.7.0/lib/execjs.rb:4:in `<top (required)>'
c:/RailsInstaller/Ruby2.3.3/lib/ruby/gems/2.3.0/gems/uglifier-4.1.10/lib/uglifier.rb:5:in `require'
c:/RailsInstaller/Ruby2.3.3/lib/ruby/gems/2.3.0/gems/uglifier-4.1.10/lib/uglifier.rb:5:in `<top (required)>'
c:/RailsInstaller/Ruby2.3.3/lib/ruby/gems/2.3.0/gems/bundler-1.15.3/lib/bundler/runtime.rb:82:in `require'
c:/RailsInstaller/Ruby2.3.3/lib/ruby/gems/2.3.0/gems/bundler-1.15.3/lib/bundler/runtime.rb:82:in `block (2 levels) in require'
c:/RailsInstaller/Ruby2.3.3/lib/ruby/gems/2.3.0/gems/bundler-1.15.3/lib/bundler/runtime.rb:77:in `each'
c:/RailsInstaller/Ruby2.3.3/lib/ruby/gems/2.3.0/gems/bundler-1.15.3/lib/bundler/runtime.rb:77:in `block in require'
c:/RailsInstaller/Ruby2.3.3/lib/ruby/gems/2.3.0/gems/bundler-1.15.3/lib/bundler/runtime.rb:66:in `each'
c:/RailsInstaller/Ruby2.3.3/lib/ruby/gems/2.3.0/gems/bundler-1.15.3/lib/bundler/runtime.rb:66:in `require'
c:/RailsInstaller/Ruby2.3.3/lib/ruby/gems/2.3.0/gems/bundler-1.15.3/lib/bundler.rb:108:in `require'
c:/Sites/myrubyblog/config/application.rb:7:in `<top (required)>'
c:/RailsInstaller/Ruby2.3.3/lib/ruby/gems/2.3.0/gems/railties-5.1.6/lib/rails/commands/server/server_command.rb:133:in `require'
c:/RailsInstaller/Ruby2.3.3/lib/ruby/gems/2.3.0/gems/railties-5.1.6/lib/rails/commands/server/server_command.rb:133:in `block in perform'
c:/RailsInstaller/Ruby2.3.3/lib/ruby/gems/2.3.0/gems/railties-5.1.6/lib/rails/commands/server/server_command.rb:130:in `tap'
c:/RailsInstaller/Ruby2.3.3/lib/ruby/gems/2.3.0/gems/railties-5.1.6/lib/rails/commands/server/server_command.rb:130:in `perform'
c:/RailsInstaller/Ruby2.3.3/lib/ruby/gems/2.3.0/gems/thor-0.20.0/lib/thor/command.rb:27:in `run'
c:/RailsInstaller/Ruby2.3.3/lib/ruby/gems/2.3.0/gems/thor-0.20.0/lib/thor/invocation.rb:126:in `invoke_command'
c:/RailsInstaller/Ruby2.3.3/lib/ruby/gems/2.3.0/gems/thor-0.20.0/lib/thor.rb:387:in `dispatch'
c:/RailsInstaller/Ruby2.3.3/lib/ruby/gems/2.3.0/gems/railties-5.1.6/lib/rails/command/base.rb:63:in `perform'
c:/RailsInstaller/Ruby2.3.3/lib/ruby/gems/2.3.0/gems/railties-5.1.6/lib/rails/command.rb:44:in `invoke'
c:/RailsInstaller/Ruby2.3.3/lib/ruby/gems/2.3.0/gems/railties-5.1.6/lib/rails/commands.rb:16:in `<top (required)>'
bin/rails:4:in `require'
bin/rails:4:in `<main>'
Bundler Error Backtrace:
from c:/RailsInstaller/Ruby2.3.3/lib/ruby/gems/2.3.0/gems/bundler-1.15.3/lib/bundler/runtime.rb:81:in `block (2 levels) in require'
from c:/RailsInstaller/Ruby2.3.3/lib/ruby/gems/2.3.0/gems/bundler-1.15.3/lib/bundler/runtime.rb:77:in `each'
from c:/RailsInstaller/Ruby2.3.3/lib/ruby/gems/2.3.0/gems/bundler-1.15.3/lib/bundler/runtime.rb:77:in `block in require'
from c:/RailsInstaller/Ruby2.3.3/lib/ruby/gems/2.3.0/gems/bundler-1.15.3/lib/bundler/runtime.rb:66:in `each'
from c:/RailsInstaller/Ruby2.3.3/lib/ruby/gems/2.3.0/gems/bundler-1.15.3/lib/bundler/runtime.rb:66:in `require'
from c:/RailsInstaller/Ruby2.3.3/lib/ruby/gems/2.3.0/gems/bundler-1.15.3/lib/bundler.rb:108:in `require'
from c:/Sites/myrubyblog/config/application.rb:7:in `<top (required)>'
from c:/RailsInstaller/Ruby2.3.3/lib/ruby/gems/2.3.0/gems/railties-5.1.6/lib/rails/commands/server/server_command.rb:133:in `require'
from c:/RailsInstaller/Ruby2.3.3/lib/ruby/gems/2.3.0/gems/railties-5.1.6/lib/rails/commands/server/server_command.rb:133:in `block in perform'
from c:/RailsInstaller/Ruby2.3.3/lib/ruby/gems/2.3.0/gems/railties-5.1.6/lib/rails/commands/server/server_command.rb:130:in `tap'
from c:/RailsInstaller/Ruby2.3.3/lib/ruby/gems/2.3.0/gems/railties-5.1.6/lib/rails/commands/server/server_command.rb:130:in `perform'

内容的提问来源于stack exchange，提问作者user8268874