for beforeunload event of turbolinks.

beforeunload_turbolinks.js.coffee

#= require jquery
#= require jquery.turbolinks
#= require turbolinks
#= require_self

returnAlert = ->
  $(document).on 'page:before-change', ->
    url = document.location.href
    if url.match('(new|edit)$')
      confirm 'Are you sure?'
    else
      $(document).off 'page:before-change'
      
$(document).ready returnAlert