title: Rails Server Could not find a JavaScript runtime
body: <p>i am getting the following error. tried to search and try to install extjs, bundler etc gems still am getting the error</p>
  
  <pre><code>harsha@harshamv:~/www/simple_cms$ rails s
  /home/harsha/.rvm/gems/ruby-2.0.0-p247/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/harsha/.rvm/gems/ruby-2.0.0-p247/gems/execjs-2.0.2/lib/execjs.rb:5:in `&lt;module:ExecJS&gt;'
      from /home/harsha/.rvm/gems/ruby-2.0.0-p247/gems/execjs-2.0.2/lib/execjs.rb:4:in `&lt;top (required)&gt;'
      from /home/harsha/.rvm/gems/ruby-2.0.0-p247/gems/uglifier-2.3.1/lib/uglifier.rb:3:in `require'
      from /home/harsha/.rvm/gems/ruby-2.0.0-p247/gems/uglifier-2.3.1/lib/uglifier.rb:3:in `&lt;top (required)&gt;'
      from /home/harsha/.rvm/gems/ruby-2.0.0-p247/gems/bundler-1.3.5/lib/bundler/runtime.rb:72:in `require'
      from /home/harsha/.rvm/gems/ruby-2.0.0-p247/gems/bundler-1.3.5/lib/bundler/runtime.rb:72:in `block (2 levels) in require'
      from /home/harsha/.rvm/gems/ruby-2.0.0-p247/gems/bundler-1.3.5/lib/bundler/runtime.rb:70:in `each'
      from /home/harsha/.rvm/gems/ruby-2.0.0-p247/gems/bundler-1.3.5/lib/bundler/runtime.rb:70:in `block in require'
      from /home/harsha/.rvm/gems/ruby-2.0.0-p247/gems/bundler-1.3.5/lib/bundler/runtime.rb:59:in `each'
      from /home/harsha/.rvm/gems/ruby-2.0.0-p247/gems/bundler-1.3.5/lib/bundler/runtime.rb:59:in `require'
      from /home/harsha/.rvm/gems/ruby-2.0.0-p247/gems/bundler-1.3.5/lib/bundler.rb:132:in `require'
      from /home/harsha/www/simple_cms/config/application.rb:7:in `&lt;top (required)&gt;'
      from /home/harsha/.rvm/gems/ruby-2.0.0-p247/gems/railties-4.0.1/lib/rails/commands.rb:74:in `require'
      from /home/harsha/.rvm/gems/ruby-2.0.0-p247/gems/railties-4.0.1/lib/rails/commands.rb:74:in `block in &lt;top (required)&gt;'
      from /home/harsha/.rvm/gems/ruby-2.0.0-p247/gems/railties-4.0.1/lib/rails/commands.rb:71:in `tap'
      from /home/harsha/.rvm/gems/ruby-2.0.0-p247/gems/railties-4.0.1/lib/rails/commands.rb:71:in `&lt;top (required)&gt;'
      from bin/rails:4:in `require'
      from bin/rails:4:in `&lt;main&gt;'
  </code></pre>