Initialize Facebook JS SDK in Coffeescript

fb_init.coffee

# Important: this requires your Facebook App ID to be in data-id on #fb-root

window.fbAsyncInit = ->
  FB.init
    appId: document.getElementById("fb-root").getAttribute("data-id")

# Async load the JS SDK
id = "facebook-jssdk"
ref = document.getElementsByTagName("script")[0]
return if document.getElementById(id)
js = document.createElement("script")
js.id = id
js.async = true
js.src = "//connect.facebook.net/en_US/all.js"
ref.parentNode.insertBefore(js, ref)