coffeescript and angular directive
Honestly, I'd recommend against creating a class. You may want classical inheritance in the future, but right now it's not necessary. Premature optimization rarely benefits anyone. Besides, if you do want classical inheritance later, it's pretty trivial to convert the code.

I'd just write it as simply as possible for now, and see what I'll actually need later:

do -&gt; # wrap in an IIFE
  # simple local variables
  isOpen      = false
  modalElem   = null
  overlayElem = null
  modal       = angular.module 'modal'

  angular.element(document).ready -&gt;
    modalElem   = document.getElementById 'modal'
    overlayElem = document.getElementById 'overlay'

  open = (attrs) -&gt;
    return if isOpen # return early
    isOpen = true

    options =
      opacity:    1
      ease:       Back.easeOut
      height:     attrs.height
      width:      attrs.width
      marginTop:  attrs.height / -2
      marginLeft: attrs.width / -2

    modalElem.style.width  = 0
    modalElem.style.height = 0
    overlayElem.style.display = 'block'
    TweenLite.to modalElem, 0.75, options

  close = -&gt;
    return unless isOpen # return early
    TweenLite.to modalElem, 0.33,
      width:      0
      height:     0
      marginTop:  0
      marginLeft: 0
      opacity:    0
      ease:       Back.easeOut
      onComplete: -&gt;
        overlayElem.style.display = 'none'
        isOpen = false # moved this here, so it flips when the modal's fully closed


  modal.directive 'openmodal', -&gt;
    (scope, element, attrs) -&gt;
      element.bind 'click', -&gt; open attrs

  modal.directive 'closemodal', -&gt;
    (scope, element, attrs) -&gt;
      element.bind 'click', -&gt; close()


If you're compiling this as a single file with CoffeeScript's default IIFE wrapper, you can skip the do -&gt; and indentation; it'll be added automatically.



If you don't want to take the approach above, here are some tips for your current code:

Using explicit return is only necessary if you want something other than the last evaluated expression to be returned. In you open/close functions, it'd be beneficial to simply return early (like I do in the code above) instead of having a big if branch.

Also, a neat trick:

getWindowDim : -&gt;
  return dim =
    height : window.innerWidth or document.documentElement.clientWidth
    width  : window.innerHeight or document.documentElement.clientHeight


can be written as

getWindowDim : -&gt;
  height : window.innerWidth or document.documentElement.clientWidth
  width  : window.innerHeight or document.documentElement.clientHeight


The return is implicit, there's no need for a variable assignment, and CoffeeScript will automatically make an object.