Respond_to in rails

Question

respond_to do |format|
  format.html
  format.xml  { render :xml => @mah_blogz }
end

respond_to do |format|
      format.js
end

Whats this respond_to, format.html, format.xml and format.js. Whats the purpose, How they work.

Answer 1

http://tinyurl.com/2a4spvs

It is a way for you to serve an, e.g., XML representation instead of an HTML one. Useful if you want to create a client not using HTML.

Answer 2

Here's the link to the documentation

http://api.rubyonrails.org/classes/ActionController/MimeResponds/InstanceMethods.html#M000386

Its a way of responding to the client based on what they are asking for, if the client asks for HTML, Rails will send back HTML to the client, if they ask for XML then XML.