rails s コマンドでエラーが出てしまう

Question

コード
```### 前提・実現したいこと

Ruby on rails でチャットアプリを作っていて久しぶりにrails sで立ち上げようとしたときにエラーが出てしまいました。初心者な為よく分からず起動できるようにアドバイスお願いいたします。

以下のコードがrails sで起動したときにでてきた結果になります。

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### 発生している問題・エラーメッセージ

MacBook-Pro:chat-space owner$ rails s
Traceback (most recent call last):
32: from bin/rails:3:in <main>' 31: from bin/rails:3:in load'
30: from /Users/owner/Desktop/projects/chat-space/bin/spring:15:in <top (required)>' 29: from /Users/owner/.rbenv/versions/2.5.1/lib/ruby/2.5.0/rubygems/core_ext/kernel_require.rb:59:in require'
28: from /Users/owner/.rbenv/versions/2.5.1/lib/ruby/2.5.0/rubygems/core_ext/kernel_require.rb:59:in require' 27: from /Users/owner/.rbenv/versions/2.5.1/lib/ruby/gems/2.5.0/gems/spring-2.1.0/lib/spring/binstub.rb:11:in <top (required)>'
26: from /Users/owner/.rbenv/versions/2.5.1/lib/ruby/gems/2.5.0/gems/spring-2.1.0/lib/spring/binstub.rb:11:in load' 25: from /Users/owner/.rbenv/versions/2.5.1/lib/ruby/gems/2.5.0/gems/spring-2.1.0/bin/spring:49:in <top (required)>'
24: from /Users/owner/.rbenv/versions/2.5.1/lib/ruby/gems/2.5.0/gems/spring-2.1.0/lib/spring/client.rb:30:in run' 23: from /Users/owner/.rbenv/versions/2.5.1/lib/ruby/gems/2.5.0/gems/spring-2.1.0/lib/spring/client/command.rb:7:in call'
22: from /Users/owner/.rbenv/versions/2.5.1/lib/ruby/gems/2.5.0/gems/spring-2.1.0/lib/spring/client/rails.rb:28:in call' 21: from /Users/owner/.rbenv/versions/2.5.1/lib/ruby/gems/2.5.0/gems/spring-2.1.0/lib/spring/client/rails.rb:28:in load'
20: from /Users/owner/Desktop/projects/chat-space/bin/rails:9:in <top (required)>' 19: from /Users/owner/Desktop/projects/chat-space/bin/rails:9:in require'
18: from /Users/owner/.rbenv/versions/2.5.1/lib/ruby/gems/2.5.0/gems/railties-5.0.7.2/lib/rails/commands.rb:18:in <top (required)>' 17: from /Users/owner/.rbenv/versions/2.5.1/lib/ruby/gems/2.5.0/gems/railties-5.0.7.2/lib/rails/commands/commands_tasks.rb:49:in run_command!'
16: from /Users/owner/.rbenv/versions/2.5.1/lib/ruby/gems/2.5.0/gems/railties-5.0.7.2/lib/rails/commands/commands_tasks.rb:85:in server' 15: from /Users/owner/.rbenv/versions/2.5.1/lib/ruby/gems/2.5.0/gems/railties-5.0.7.2/lib/rails/commands/commands_tasks.rb:85:in tap'
14: from /Users/owner/.rbenv/versions/2.5.1/lib/ruby/gems/2.5.0/gems/railties-5.0.7.2/lib/rails/commands/commands_tasks.rb:88:in block in server' 13: from /Users/owner/.rbenv/versions/2.5.1/lib/ruby/gems/2.5.0/gems/railties-5.0.7.2/lib/rails/commands/commands_tasks.rb:88:in require'
12: from /Users/owner/Desktop/projects/chat-space/config/application.rb:7:in <top (required)>' 11: from /Users/owner/.rbenv/versions/2.5.1/lib/ruby/gems/2.5.0/gems/bundler-2.1.4/lib/bundler.rb:174:in require'
10: from /Users/owner/.rbenv/versions/2.5.1/lib/ruby/gems/2.5.0/gems/bundler-2.1.4/lib/bundler/runtime.rb:58:in require' 9: from /Users/owner/.rbenv/versions/2.5.1/lib/ruby/gems/2.5.0/gems/bundler-2.1.4/lib/bundler/runtime.rb:58:in each'
8: from /Users/owner/.rbenv/versions/2.5.1/lib/ruby/gems/2.5.0/gems/bundler-2.1.4/lib/bundler/runtime.rb:69:in block in require' 7: from /Users/owner/.rbenv/versions/2.5.1/lib/ruby/gems/2.5.0/gems/bundler-2.1.4/lib/bundler/runtime.rb:69:in each'
6: from /Users/owner/.rbenv/versions/2.5.1/lib/ruby/gems/2.5.0/gems/bundler-2.1.4/lib/bundler/runtime.rb:74:in block (2 levels) in require' 5: from /Users/owner/.rbenv/versions/2.5.1/lib/ruby/gems/2.5.0/gems/bundler-2.1.4/lib/bundler/runtime.rb:74:in require'
4: from /Users/owner/.rbenv/versions/2.5.1/lib/ruby/gems/2.5.0/gems/uglifier-4.2.0/lib/uglifier.rb:5:in <top (required)>' 3: from /Users/owner/.rbenv/versions/2.5.1/lib/ruby/gems/2.5.0/gems/uglifier-4.2.0/lib/uglifier.rb:5:in require'
2: from /Users/owner/.rbenv/versions/2.5.1/lib/ruby/gems/2.5.0/gems/execjs-2.7.0/lib/execjs.rb:4:in <top (required)>' 1: from /Users/owner/.rbenv/versions/2.5.1/lib/ruby/gems/2.5.0/gems/execjs-2.7.0/lib/execjs.rb:5:in module:ExecJS'
/Users/owner/.rbenv/versions/2.5.1/lib/ruby/gems/2.5.0/gems/execjs-2.7.0/lib/execjs/runtimes.rb:58:in `autodetect': Could not find a JavaScript runtime. See https://github.com/rails/execjs for a list of available runtimes. (ExecJS::RuntimeUnavailable)

### 該当のソースコード

```ここに言語名を入力
ソースコード

試したこと

補足情報（FW/ツールのバージョンなど）

ここにより詳細な情報を記載してください。

Answer 1

Javascriptのランタイムがないエラーについては、
最初の方の回答のようにGemのランタイムで解決する方法と、
Node.js をインストールしておく方法があります。

お好きな方法をどうぞ。

Answer 2

同じ原因か分かりませんが、Exec-JS のランタイムが利用できないようなので以下のページが参考にならないでしょうか？

ExecJS::RuntimeUnavailableの解決方法 - Qiita

gem 'mini_racer'

をbundle installしよう。