New Twiddle

controllers.application.js

import Ember from 'ember';

export default Ember.Controller.extend({
  volatile: Ember.computed('counter', function() {
    return this.get('counter');
  }).volatile(),
  
  counter: 0,
  
  actions: {
    incrementCounter() {
      this.incrementProperty('counter');
    }
  }
});

templates.application.hbs

volatile: {{volatile}}
<br>
counter: {{counter}}
<br>

<button onclick={{action "incrementCounter"}}>increment counter</button>

twiddle.json

{
  "version": "0.13.0",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/1.11.3/jquery.js",
    "ember": "2.16.2",
    "ember-template-compiler": "2.16.2",
    "ember-testing": "2.16.2"
  },
  "addons": {
    "ember-data": "2.16.3"
  }
}