title: Rails Js, Render page in page
body: <p>I don't know how it exactly called, but as an example.</p>
  
  <p>I have possibility to create post, and I have 2 buttons - "Save" and "Preview".</p>
  
  <p>I want to when user click on "Preview" user not leaving page, but with JS it's render right after buttons new html with post view.</p>
  
  <p>Can you give me general idea how it's done?</p>