New Twiddle

controllers.application.js

import Ember from 'ember';

export default Ember.Controller.extend({
  outputKeys: Ember.computed(function(){
    var ret = [];
    for(var a in []){
      ret.push(a);
    }
    return ret;
  })
});

templates.application.hbs

{{#each outputKeys as |key|}}
	<pre><code>{{key}}</code></pre>
{{/each}}

twiddle.json

{
  "version": "0.12.1",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/1.11.3/jquery.js",
    "ember": "2.12.0",
    "ember-template-compiler": "2.12.0",
    "ember-testing": "2.12.0"
  },
  "addons": {
    "ember-data": "2.12.1"
  }
}