How to use oncomplete in Rails-3.2.1 Ajax

I’m using Rails-3.2.1 and working on ajax.

Below is my code and I want to add woking in progress msg while my
function is in progress.

======================================================================
example.html.erb file

Once you approve it will publish.   [  <%= link_to "Approve", {:action=>"approve_status", :id=>params[:id], :stat=>"approved"}, :remote=>true %>   |   <%= link_to "Reject", {:action=>"approve_status", :id=>params[:id], :stat=>"rejected"}, :remote=>true %>  ]

controller method

def approve_status
@camp_id = params[:id]
@camp_stat = params[:stat]

@campaign = Campaign.find_by_id(@camp_id)
@campaign.approved_status = @camp_stat

end

======================================================================
example.js.erb file

jQuery.noConflict();
jQuery("#showmsg").hide();
jQuery("#app_stat").html("<%= @camp_stat %>");

How to use ajax complete or success in this?