doitian/app.js.coffee

## app.js.coffee
class App

  constructor: (@body) ->
    # site global setup

  start: ->
    controllerName = @body.data('js_controller')
    Controller = App[controllerName]
    if Controller
      @main = new Controller
    @

window.App = App

$ ->
  window.app = app = new App($('body'))
  app.start()

## application.html.erb
<body data-js_controller="<%= js_controller %>">
  ...
</body>

## application_controller.rb
# Default JS controller for all actions in current Rails controller
# Set a new value or get current value
def self.js_controller(new_value = nil)
  @js_controller = new_value || @js_controller || self.name.sub(/Controller$/, '').gsub(/::/, /-/)
end

# Lets each action customize it
attr_writer :js_controller

# If action does not set a value, use controller default value
def js_controller
  @js_controller || self.class.js_controller
end
helper_method :js_controller

## welcome.js.coffee
class App.Welcome

  constructor: ->
    # setup

## welcome_controller.rb
class WelcomeController < ApplicationController
  js_controller 'Welcome'

  def new
    # use default 'Welcome' js controller
  end

  def create
    # use a different controller
    self.js_controller = 'WelcomeCreate'
  end
end
	class App

	constructor: (@body) ->
	# site global setup

	start: ->
	controllerName = @body.data('js_controller')
	Controller = App[controllerName]
	if Controller
	@main = new Controller
	@

	window.App = App

	$ ->
	window.app = app = new App($('body'))
	app.start()
	# Default JS controller for all actions in current Rails controller
	# Set a new value or get current value
	def self.js_controller(new_value = nil)
	@js_controller = new_value \|\| @js_controller \|\| self.name.sub(/Controller$/, '').gsub(/::/, /-/)
	end

	# Lets each action customize it
	attr_writer :js_controller

	# If action does not set a value, use controller default value
	def js_controller
	@js_controller \|\| self.class.js_controller
	end
	helper_method :js_controller
	class WelcomeController < ApplicationController
	js_controller 'Welcome'

	def new
	# use default 'Welcome' js controller
	end

	def create
	# use a different controller
	self.js_controller = 'WelcomeCreate'
	end
	end