New Twiddle

controllers.application.js

import Ember from 'ember';
var Person = Ember.Object.extend({
  init() {
  
  },
});
export default Ember.Controller.extend({
  appName: 'Add Observer To Object',
  init: function(){
    console.log('init');
    var p1 = Person.create();
    var p2 = Person.create();
    p1.addObserver('name', function(){
      console.log('observer ran', this.get('name'));
    });
    p1.set('name', 'bart');
    p2.set('name', 'simpson');
    
                   
  }
});

templates.application.hbs

<h1>Welcome to {{appName}}</h1>
<br>
<br>
{{outlet}}
<br>
<br>

twiddle.json

{
  "version": "0.10.5",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/1.11.3/jquery.js",
    "ember": "2.8.0",
    "ember-data": "2.8.0",
    "ember-template-compiler": "2.8.0",
    "ember-testing": "2.8.0"
  },
  "addons": {}
}