jQuery double submit prevention. Originally from http://thepugautomatic.com/2008/07/jquery-double-submission/.

jquery.prevent_double_submit.js.coffee

# $("form:not([data-remote])").preventDoubleSubmit()
# http://henrik.nyh.se/2008/07/jquery-double-submission/

$ = jQuery

$.fn.preventDoubleSubmit = ->
  ESC_KEYCODE = 27
  form = this[0]

  # Unprevent on ESC.
  $(document).keyup (e) ->
    if e.keyCode == ESC_KEYCODE
      form.beenSubmitted = false

  $(form).submit ->
    if @beenSubmitted
      return false
    else
      @beenSubmitted = true
      return true