New Twiddle

controllers.application.js

import Ember from 'ember';

export default Ember.Controller.extend({
  appName: 'Ember Twiddle',
  
  property1: undefined,
  property2: null,
  
  unknownProperty(key) {
    console.log('Trying to get unknownProperty', key);
  },
  
  actions: {
    getWithDefault(propertyName) {
      console.log('getWithDefault', this.getWithDefault(propertyName, 'I AM DEFAULT'));
    },
  }
});

templates.application.hbs

<h1><code>undefined</code> || <code>null</code></h1>

<button onclick={{action 'getWithDefault' 'property1'}}>
  getWithDefault 'property1'
 </button>
 
<button onclick={{action 'getWithDefault' 'property2'}}>
  getWithDefault 'property2'
 </button>

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"
  }
}