Listing 3. app.coffee

$(document).ready ->

   changeSize = ->
       text = $(this)

       if text.hasClass "small"
           text.removeClass "small"
           text.addClass "medium"

       else if text.hasClass "medium"
           text.removeClass "medium"
           text.addClass "large"

       else if text.hasClass "large"
           text.removeClass "large"
           text.addClass "small"

       else
           text.addClass "large"

       true

   ($ "p").addClass "large"
   ($ "p").live 'click', changeSize