title: Send data from js to rails
body: <p>I have a variable on controller in my project. 
  I want to send variable from controller to js,
  Variable is  calculate again on js and send from js to controller. but I'm failing. How can i do it? Thank you from now.</p>
  
  <pre><code>  %input#calculate{ type: 'text', value: "#{@cpp}", disabled: true }/
  </code></pre>
  
  <p>@cpp variable is send to js. It calculate again. Print on the screen new value. but @cpp value doen not change.</p>