My twiddle

controllers.application.js

import Ember from 'ember';

export default Ember.Controller.extend({
  appName: 'Ember Twiddle',
  items: [],
  i: 1,
  isAnimating: false,
  
  actions: {
    addItem: function() {
      this.get('items').pushObject({id: this.get('i')});
      Ember.run.next(this, this.animate);
    }
  },
  
  animate: function() {
    var self = this;
    this.set('isAnimating', true);
    
    let $item = Ember.$('#image-' + this.get('i'));
    Ember.$.Velocity($item, {
      translateX: ["0px", "50px"],
      opacity: 1
    }).then(function() {
      self.incrementProperty('i');
    	self.set('isAnimating', false);
    });
  }
});

helpers.my-helper.js

import Ember from 'ember';

export function myHelper([item]/*, hash*/) {
  return Ember.String.htmlSafe('<div id="image-'+ item.id +'" class="image"></div>');
}

export default Ember.Helper.helper(myHelper);

styles.app.css

body {
  margin: 12px 16px;
  font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif;
  font-size: 12pt;
}

.image {
  width: 30px;
  height: 30px;
  background-image: url("https://cdnjs.cloudflare.com/ajax/libs/emojione/2.2.5/assets/png/1f603.png");
  background-size: 100% 100%;
  display: inline-block;
  opacity: 0;
}

templates.application.hbs

<h1>Welcome to {{appName}}</h1>
<br>
<br>
<button {{action "addItem"}} disabled={{isAnimating}}>Add item to array</button>
<br>
<br>
{{#each items as |item|}}
  {{my-helper item}}
{{/each}}
<br>
<br>

twiddle.json

{
  "version": "0.10.5",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/1.11.3/jquery.js",
    "ember": "1.13.13",
    "ember-data": "1.13.15",
    "ember-template-compiler": "1.13.13",
    "ember-testing": "1.13.13"
  },
  "addons": {
  	"liquid-fire": "0.23.1"
  }
}