emerson up and running in rails >= 3.2

application.js

//  .... require all the things you need
// Vendored requires
//= require jquery
//= require underscore
//= require emerson

// Application requires
//= require base
//= require_tree ./lib/traits
//= require_tree ./lib/views

base.js

(function($, window) {
  $(window).load(function() {
    Emerson.init();
  });

})(jQuery, this);

Gemfile

gem 'emerson'

lib-traits-alerter.js

(function($, define) {
  var trait = define('alerter', {
    initialize : function initialize() {
      console.log("initializing trait!");
    },

    subscribe : {
      'mouseout' : function handler(e) {
        this.alertMethod();
      }
    }
  });

  trait.extend({
    alertMethod : function alertMethod() {
      alert("you moused out");
    }
  });
})(Emerson.base, Emerson.trait);

page.html

<p>
  Here is some text. 
  <span data-traits='alerter'>I should alert when you mouse out!</span>
</p>