画像を一回だけ読み込むやつ

imageloader.coffee

class ImageLoader
  map = {}
  constructor: (@src)->
    if not map[@src]
      @dfd = new $.Deferred
      map[@src] = @
    return map[@src]
  
  load: ->
    img = new Image
    img.src = @src
    img.onload = =>
      @dfd.resolve img
    @load = =>
      do @dfd.promise
    do @load