index.html

<button id="addNewObserver">Add New Observer checkbox</button>
<input id="mainCheckbox" type="checkbox">
<div id="observersContainer"></div>

observer.coffee

ObserverList = ->
	@.observerList = []
	return


ObserverList::Add = ( obj )->
	@.observerList.push obj
	return


ObserverList::Empty = ->
	@.observerList = []
	return


ObserverList::Count = ->
	@.observerList.length
	return


ObserverList::Get = ( index )->
	if index > -1 and index < @.observerList.length
		@.observerList[ index ]
	return


ObserverList::Insert = ( obj, index )->
	pointer = -1

	if index is 0
		@.observerList.unshift obj
		pointer = index
	else if index is @.observerList.length
		@.observerList.push obj
		pointer = index

	return pointer


ObserverList::IndexOf = ( obj, startIndex)->
	i = startIndex
	pointer = -1

	while i < @.observerList.length
		if @.observerList[i] is obj
			pointer = i
		i++

	return pointer


ObserverList::RemoveIndexAt = ( index )->
	if index is 0
		@.observerList.shift()
	else if index is @.observerList.length-1
		@.observerList.pop()
	return


extend = ( obj, extension )->
	for key of obj
		extension[key] = obj[key]
	return


###################################################


Subject = ->
	@.observers = new ObserverList()
	return

Subject::AddObserver = ( observer )->
	@.observers.Add observer
	return

Subject::RemoveObserver = ( observer )->
	@.observers.RemoveIndexAt @.observers.IndexOf observer, 0
	return

Subject::Notify = ( context )->
	observerCount = @.observers.Count()
	i=0
	while i < observerCount
		@.observers.Get(i).Update context
		i++
	return


Observer = ->
	@.Update = ->
	return


###################################################


controlCheckbox = document.getElementById 'mainCheckbox'
addBtn = document.getElementById 'addNewObserver'
container = document.getElementById 'observersContainer'

extend new Subject(), controlCheckbox

addNewObserver = ->
	check = document.createElement 'input'
	check.type = 'checkbox'

	extend new Observer(), check

	check.Update = ( value )->
		@.checked = value
		return

	controlCheckbox.AddObserver check

	container.appendChild check
	return


controlCheckbox['onclick'] = new Function "controlCheckbox.Notify(controlCheckbox.checked)"
addBtn['onclick'] = addNewObserver