Drag Event handler class

dragevents.coffee

window.DragEventHandler = (containers) ->
  focused = false

   this.windowDragoverOn = ->
    unless focused
      focused = true
      for container in containers
        container.classList.add('window-dragover')

   this.windowDragoverOff = ->
    if focused
      focused = false
      for container in containers
        container.classList.remove('window-dragover')

   addEvent = (obj, evt, fn) ->
    if obj.addEventListener
      obj.addEventListener(evt, fn, false)
    else if obj.attachEvent
      obj.attachEvent("on" + evt, fn)

   this.init = ->
    addEvent window, 'dragover', (event) =>
      event = event ? event : window.event
      event.preventDefault()
      this.windowDragoverOn()

     addEvent window, 'drop', (event) =>
      event = event ? event : window.event
      event.preventDefault()
      this.windowDragoverOff()

     addEvent document, 'mouseout', (event) =>
      event = event ? event : window.event
      from = event.relatedTarget || event.toElement
      if (!from || from.nodeName == "HTML")
        this.windowDragoverOff()

   this.init()

   return this