rails 4 Could not find a JavaScript runtime (ExecJS::RuntimeUnavailable)

chen@chen-pc ~/demo/abc/bin $ rails c
/home/chen/.rvm/gems/ruby-2.0.0-p451/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/chen/.rvm/gems/ruby-2.0.0-p451/gems/execjs-2.0.2/lib/execjs.rb:5:in `<module:ExecJS>'

have something wrong on rails server.

sudo apt-get install python-software-properties
sudo add-apt-repository ppa:chris-lea/node.js
sudo apt-get update
sudo apt-get install nodejs

on success