ruby on rails - Is it possible to refresh partial frequently using Ajax?

Question

In background, I want it to reload and shows the number how many unread messages are there.
I want that without refreshing page. I mean using ajax.

If I had this in menu, how can I refresh only this section every 30 secs?

<li><%= link_to sanitize('<i class="icon-envelope"></i> ') + "received messages" + sanitize(' <span class="badge badge-info">'+current_user.mailbox.inbox(:read => false).count(:id, :distinct => true).to_s+'</span>'), messages_received_path  %></li>

messages_controller.rb

  def received
    if params[:search]
     @messages = current_user.mailbox.inbox.search_messages(@search).page(params[:page]).per(10)
    else
     @messages = current_user.mailbox.inbox.page(params[:page]).per(10)
    end 
     add_crumb 'Messages Received', messages_received_path

     @box = 'inbox'
     render :index
  end

UPDATE:_______________________________

assets/javascript/refresh_messages_count.js

$(document).ready(function () {
    // will call refreshPartial every 3 seconds
    setInterval(refreshPartial, 3000)

});

function refreshPartial() {
  $.ajax({
    url: "messages/refresh_part";
 })
}

messages_controller.rb

def refresh_part
    @message_count = current_user.mailbox.inbox(:read => false).count(:id, :distinct => true)

    # get whatever data you need to a variable named @data 
    respond_to do |format| 
        format.js {render :action=>"refresh_part.js"} 
    end

end

views/layouts/_menu.html.erb

<span id="message_received_count"><%= render :partial => "layouts/message_received_count" %></span>

views/layouts/_message_received_count.html.erb

<% if user_signed_in? && current_user.mailbox.inbox(:read => false).count(:id, :distinct => true) > 0 %>
 <li><%= link_to sanitize('<i class="icon-envelope"></i> ') + "Received" + sanitize(' <span class="badge badge-info">'+@message_count.to_s+'</span>'), messages_received_path  %></li>
<% else %>
 <li><%= link_to sanitize('<i class="icon-envelope"></i> ') + "Received", messages_received_path  %></li>
<% end %>

views/messages/refresh_part.js.erb

$('#message_received_count').html("#{escape_javascript(render 'layouts/messages_received_count', data: @message_count)}");

Answer 1

You will use setInterval to send the ajax request:

$(document).ready(function () {
    // will call refreshPartial every 3 seconds
    setInterval(refreshPartial, 3000)

});

// calls action refreshing the partial
function refreshPartial() {
  $.ajax({
    url: "whatever_controller/refresh_part"
 })
}

Then you make an action in a controller like this:

def refresh_part
  # get whatever data you need to a variable named @data
  respond_to do |format|
    format.js
  end
end

then you will write a js file named refresh_part.js.haml (you could erb instead of haml).

refresh_part.js.haml would look like this:

$('#part_you_want_to_refresh').html("#{escape_javascript(render 'name_of_partial', data: @data)}");

make sure you set the correct routes in routes.rb.