New Twiddle

controllers.application.js

import Ember from 'ember';

export default Ember.Controller.extend({
  appName: 'Ember Twiddle',
  someArr: [1,2,3],
  computedArr: Ember.computed('someArr', function(key, value) {
    if(arguments.length > 1) {
      return value;
    }
    
    // return a copy of the array
    return this.get('someArr').slice();
  }),
  
  actions: {
  	setComputedVal: function() {
      var computedArr = this.get('computedArr');
      
      computedArr.pushObject(2);
    	this.set('computedArr', computedArr);
      
      console.log(this.get('computedArr'));
      console.log(this.get('someArr'));
    },
    save: function(){
      this.set('someArr', this.get('computedArr'));
      console.log(this.get('someArr'));
    }
  }
});

templates.application.hbs

<h1>Appname {{appName}}</h1>
<br>
<br>
{{outlet}}

<button onclick={{action "setComputedVal"}}>set</button>
<button onclick={{action "save"}}>save</button>
<br>
<br>

twiddle.json

{
  "version": "0.7.2",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "use_pods": false,
    "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/2.4.4/ember.debug.js",
    "ember-data": "https://cdnjs.cloudflare.com/ajax/libs/ember-data.js/2.4.3/ember-data.js",
    "ember-template-compiler": "https://cdnjs.cloudflare.com/ajax/libs/ember.js/2.4.4/ember-template-compiler.js"
  }
}