Mapping debugging

controllers.application.js

import Ember from 'ember';

let RowItem = Ember.Object.extend({
	order: 0
});

export default Ember.Controller.extend({
  appName: 'Ember Twiddle',
  sortDirection: '',
  items: Ember.computed(function(){
  	return Ember.A([
      RowItem.create({order:1}),
      RowItem.create({order:2}),
      RowItem.create({order:3}),
    ]);
  }),
  sortedItems: Ember.computed('items', 'sortDirection', function(){
    let items = this.get('items');
    if (this.get('sortDirection') === '') {
      let mappedItems = items.mapBy('order');
      console.log('going to return default sorted items, it should be 1, 2, 3');
      console.log('mapped items:', mappedItems);
      
    	return items;
    }
  	let result = this.get('items').sort(function(a, b) {
    	return a.get('order') - b.get('order');
    });
    if (this.get('sortDirection') === 'desc') {
    	return result.slice().reverse();
    } else {
      return result;
    }
  }),
  actions: {
    resetSort() {
    	this.set('sortDirection', '');
    },
     sort() {
      if (this.get('sortDirection') === 'desc') {
        this.set('sortDirection', 'asc');
      } else {
          this.set('sortDirection', 'desc');
      }
     } 
  }
});

templates.application.hbs

<h1>Try click on "Sort" to get (3,2,1) and "Reset sorting"</h1>

<p>
Problem: mapBy on array not persistent
<br>
Given: <br>
* array of emberObjects, named "items". (for example, user list)<br>
* each item has "order" property<br>
* sortedItems - computed property, depended on "array", "sortDirection"<br>
<br>

How to reproduce:<br>
1.) Open gist.<br>
2.) By default no ordering for sortedItems<br>
3.) Click on "Sort" button. Now "sortedItems" has logic to return sorted array, instead of original "list"<br>
4.) Click on "Reset" button to get "original" sort (no sort).<br>
<br>
--== ERROR ==--<br>
<br>
Expected result:
<br>
"sortedItems" ordering must equal "Items" ordering
<br>
Output:
<br>
sortedItems has prev sort result, even for "list".mapBy('order') - is should return 1,2,3 but returns 3,2,1 

</p>
<br>
<br>
{{outlet}}
<br>
<ul>
{{#each sortedItems as |item|}}
	<li>{{item.order}}</li>
{{/each}}
</ul>

<button {{action 'sort'}}>Sort {{sortDirection}}</button>

<button {{action 'resetSort'}}>Reset sorting</button>

twiddle.json

{
  "version": "0.13.1",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/1.11.3/jquery.js",
    "ember": "2.16.2",
    "ember-template-compiler": "2.16.2",
    "ember-testing": "2.16.2"
  },
  "addons": {
    "ember-data": "2.16.3"
  }
}