`window.onbeforeunload` with TurboLinks support.

turbolinks-unloader.js

var Unloader = (function() {
  var handlers = [];

  var runNative = function() {
    return findMessage();
  };

  var findMessage = function() {
    var message;
    for(var i = 0; i < handlers.length; i++) {
      message = handlers[i]();

      if(message) break;
    }
    return message;
  };

  var runTurboLinks = function(e) {
    var message = findMessage(),
        confirmResult;
    if(message) {
      confirmResult = confirm(message);
      if(confirmResult) {
        handlers = [];
      }
      return confirmResult;
    }
    else {
      handlers = [];
      return true;
    }
  };

  var clearOnce = function() {
    once = [];
  };

  var Unloader = {
    init: function() {
      window.onbeforeunload = runNative;
      $(window).on('page:before-change', runTurboLinks);
    },
    register: function(fn) {
      handlers.push(fn);
    },
    unregister: function(fn) {
      for(var i = 0; i < handlers.length; i++) {
        if(handlers[i] == fn) {
          handlers.splice(i, 1);
        }
      }
    }
  };

  return Unloader;
})();

This looks nice. So to use it, you'd start with

Unloader.register -> if true then "Are you sure?"

Doesn't IE8 need some special handling, with setting e.returnValue? http://stackoverflow.com/questions/1119289/how-to-show-the-are-you-sure-you-want-to-navigate-away-from-this-page-when-ch

Hmm, wasn't able to get this to work

$('form[data-check-form]').each ->
      $this = $(this)
      form_clean = $this.serialize()
      Unloader.register -> "Not clean" if $this.serialize() != form_clean

Am I doing something wrong?