application.controller.js

import Ember from 'ember';

window.list = null;

export default Ember.Controller.extend({
  appName:'Ember Twiddle',
  
  list: [Ember.Object.create({name: 'alpha'}), Ember.Object.create({name: 'bravo'}), Ember.Object.create({name: 'charlie'})],
  
  cmp: Ember.computed('[email protected]', function() {
    console.log('hi');
    
    window.list = this.get('list');
    
    if (window.list.get('firstObject.name') == 'alice3') {
      debugger;
    }
    
    return this.get('list').map(function(v) {
      return v.get('name');
    });
  })
});

setTimeout(function() {
  window.list.get('firstObject').set('name', 'alice3');
}, 3000);

application.template.hbs

<h1>Welcome to {{appName}}</h1>
<br>
<br>
{{this.cmp}}
{{outlet}}
<br>
<br>

twiddle.json

{
  "version": "0.5.0",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/1.11.3/jquery.js",
    "ember": "https://cdnjs.cloudflare.com/ajax/libs/ember.js/2.2.0/ember.debug.js",
    "ember-data": "https://cdnjs.cloudflare.com/ajax/libs/ember-data.js/2.2.0/ember-data.js",
    "ember-template-compiler": "https://cdnjs.cloudflare.com/ajax/libs/ember.js/2.2.0/ember-template-compiler.js"
  }
}