Drop detection based on https://gist.github.com/2907187

jquery.drop.coffee

do (jQuery) ->

  $ = jQuery
  
  wrap = (fn) ->
    (e) ->
      fn e
      do e.stopPropagation
      do e.preventDefault
      false
   
  $.fn.dropArea = ->
    @on
      dragenter: wrap (e) -> 
        $(e.target).addClass "dragOver"
      dragover: wrap (e) -> 
        e.originalEvent.dataTransfer.dropEffect = "copy"
      dragleave: wrap (e) -> 
        $(e.target).removeClass "dragOver"