Debugging this jade+coffeescript code on Express4 server - node.js

Question

I am looking for some help as I don't know how bad those lines of codes are.
I am trying to adapt this original Codepen.io work (http://codepen.io/ettrics/pen/Jdjdzp/ , by Ettrics) for one of my teaching project. I run my web page on a Express4+Stylus+Coffescript Node's server.
The CoffeeScript file:
# Each popup takes the entire window, so it is a modal
Modal = ->
# Make it easier for yourself by not having to type as much to select an element (QuerySelectorAll)
$qsa = (el) ->
document.querySelectorAll(el)
trigger = $qsa('.modal__trigger') # What you click to activate the modal
modals = $qsa('.modal') # The entire modal (takes up entire window)
modalsbg = $qsa('.modal__bg') # The entire modal (takes up entire window)
content = $qsa('.modal__content') # The inner content of the modal
closers = $qsa('.modal__close') # An element used to close the modal
isOpen = false
contentDelay = 100 # Duration after you click the button and wait for the content to show
len = trigger.length
getId = (event) ->
event.preventDefault()
# Get the value of the data-modal attribute from the button
modalId = this.dataset.modal
# Remove the '#' from the string
len = modalId.length
modalId = modalId.substring(1, len)
# Select the modal we want to activate
modal = document.getElementById(modalId)
# Execute function that creates the temporary expanding div named fakeDiv
makefakeDiv(this, modal)
makefakeDiv = (self, modal) ->
fakeDiv = document.getElementById('modal__temp');
# If there isn't a 'fakeDiv', create one and append it to the button that was
# clicked. after that execute the function 'moveTrigger' which handles the animations.
if fakeDiv?
fakeDiv = document.createElement('div')
fakeDiv.id = 'modal__temp'
self.appendChild(fakeDiv)
moveTrigger(self, modal, fakeDiv)
moveTrigger = (trigger, modal, div) ->
triggerProps = trigger.getBoundingClientRect()
modalProps = modal.querySelector('.modal__content').getBoundingClientRect()
xc = window.innerWidth / 2
yc = window.innerHeight / 2
######## VOIR LE CSS !!
# This class increases z-index value so the button goes overtop the other buttons
trigger.classList.add('modal__trigger--active')
# These values are used for scale the fakeDiv div to the same size as the modal
scaleX = modalProps.width / triggerProps.width
scaleY = modalProps.height / triggerProps.height
scaleX = scaleX.toFixed(3) # Round to 3 decimal places
scaleY = scaleY.toFixed(3)
# These values are used to move the button to the center of the window (to pepare the ease out effect)
transX = Math.round(xc - triggerProps.left - triggerProps.width / 2)
transY = Math.round(yc - triggerProps.top - triggerProps.height / 2)
# If the modal is aligned to the top then move the button to the center-y of the modal instead of the window
if modal.classList.contains('modal--align-top')
transY = Math.round(modalProps.height / 2 + modalProps.top - triggerProps.top - triggerProps.height / 2)
# Translate button to center of screen
trigger.style.transform = 'translate(' + transX + 'px, ' + transY + 'px)'
trigger.style.webkitTransform = 'translate(' + transX + 'px, ' + transY + 'px)'
# Expand fakeDiv to the same size as the modal
div.style.transform = 'scale(' + scaleX + ',' + scaleY + ')';
div.style.webkitTransform = 'scale(' + scaleX + ',' + scaleY + ')'
# Smart animation API used to open
window.setTimeout( ->
window.requestAnimationFrame(open(modal, div))
, contentDelay)
open = (modal, div) ->
if !isOpen
# Select the content inside the modal
content = modal.querySelector('.modal__content')
# Reveal the modal
modal.classList.add('modal--active')
# Reveal the modal content
content.classList.add('modal__content--active')
###
# When the modal content is finished transitioning, fadeout expanding
# fakeDiv so when the window resizes it isn't visible ( it doesn't
# move with the window).
###
content.addEventListener('transitionend', hidefakeDiv, false)
isOpen = true
hidefakeDiv = ->
# Fadeout fakeDiv so that it can't be seen when the window is resized
div.style.opacity = '0'
content.removeEventListener('transitionend', hidefakeDiv, false)
close = (event) ->
event.preventDefault()
event.stopImmediatePropagation()
target = event.target
div = document.getElementById('modal__temp')
###
# Make sure the modal__bg or modal__close was clicked, we don't
# want to be able to click inside the modal and have it close.
###
if isOpen and target.classList.contains('modal__bg') or target.classList.contains('modal__close')
# Make the hidden div visible again and remove the transforms so it scales back to its original size
div.style.opacity = '1'
div.removeAttribute('style')
###
# Iterate through the modals, modal contents and triggers to remove their active classes.
# Remove the inline css from the trigger to move it back into its original position.
###
for i in [0..len]
modals[i].classList.remove('modal--active')
content[i].classList.remove('modal__content--active')
trigger[i].style.transform = 'none'
trigger[i].style.webkitTransform = 'none'
trigger[i].classList.remove('modal__trigger--active')
# When fakeDiv opacity is 1 again, we want to remove it from the dom
div.addEventListener('transitionend', removeDiv, false)
isOpen = false
removeDiv = ->
setTimeout( ->
window.requestAnimationFrame(div.remove())
, contentDelay - 50)
bindActions = ->
for i in [0..len]
trigger[i].addEventListener('click', getId, false)
closers[i].addEventListener('click', close, false)
modalsbg[i].addEventListener('click', close, false)
init = ->
bindActions()
{init: init}
window.onload = Modal.init
This coffeescript file is called in jade by
script(src='javascripts/coffee-script.js')
script(src='javascripts/modal.coffee', type='text/coffeescript')
I could not use the CoffeeScript compiler logs because the of the 'window.onload = Modal.init' which returned a "window is not defined" error. But browser console returns no error, Codepen neither.
I have to confess that I began to learn these 4 languages 3 days ago. So I basically don't know anything about anything... I don't even know if my app settings are right.
Can anyone give me a hand on this?
Thanks a lot! :)