New Twiddle

components.my-component.js

import Ember from 'ember';

export default Ember.Component.extend({
  contents: [],
  
  pushContents() {
    this.get('contents').pushObject('hello');
  }
});

controllers.application.js

import Ember from 'ember';

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

templates.application.hbs

<h1>Welcome to {{appName}}</h1>
<br>
<br>
{{outlet}}

{{my-component}}
{{my-component}}
{{my-component}}
<br>
<br>

templates.components.my-component.hbs

{{contents}}

<button {{action 'pushContents'}}>Click</button>

twiddle.json

{
  "version": "0.15.0",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.js",
    "ember": "3.2.2",
    "ember-template-compiler": "3.2.2",
    "ember-testing": "3.2.2"
  },
  "addons": {
    "ember-data": "3.2.0"
  }
}