New Twiddle

components.my-component.js

import Ember from 'ember';

export default Ember.Component.extend({
  items: [],
  
  actions: {
    addItem(item) {
      this.get('items').pushObject(item);
    },
  }
});

controllers.application.js

import Ember from 'ember';

export default Ember.Controller.extend({
  appName: 'Ember Twiddle'
});

templates.application.hbs

<h3>List One</h3>
{{my-component}}
<h3>List Two</h3>
{{my-component}}

templates.components.my-component.hbs

<ul>
{{#each items as |item|}}
  <li>{{item}}</li>
{{/each}}
</ul>
{{input value=value}}<button onclick={{action "addItem" value}}>Add</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"
  }
}