jQuery conditional scriptloader implementation in coffeescript. Inspired by http://stackoverflow.com/a/7617196/111363.

scriptloader.coffee

class ScriptLoader

  @::libraries =
    jQuery: "//ajax.googleapis.com/ajax/libs/jquery/$version/jquery.js"

  constructor: (options...) ->

    [lib, @version, @compressed] = options
    if @libraries[lib] then @lib = @libraries[lib]

  load: (callback) ->

    loadCallback = ->
      @loaded = true
      callback()

    s = document.createElement 'script'
    s.onload = loadCallback
    s.onreadystatechange = ->
      if not @loaded and /loaded|complete/.test s.readyState
        loadCallback()

    s.src = @lib.replace('$version', @version)
    if @compressed then @lib = @lib.replace('.js', '.min.js')

    (document.getElementsByTagName('head')?[0] or document.body).appendChild s

unless jQuery?
  jQueryLoader = new ScriptLoader 'jQuery', '1.9.1', true
  jQueryLoader.load ->
    console.log 'my callback'