Ember Riddle

components.my-list.js

import Ember from 'ember';

export default Ember.Component.extend({
  count: 0,
  items: [],
 
  actions: {
    add() {
      this.incrementProperty('count');
      this.get('items').pushObject(`item #${this.count}`);
    }
  }
});

controllers.application.js

import Ember from 'ember';

export default Ember.Controller.extend({
});

templates.application.hbs

<h1>Ember Puzzle</h1>
<br>
<br>

<div>
  {{my-list}}
  <br>
  {{!-- {{my-list}} --}}
</div>

templates.components.my-list.hbs

({{count}})
<button {{action "add"}}>Add</button>
<ul>
  {{#each items as |item|}}
    <li>{{item}}</li>
  {{else}} 
    no items
  {{/each}}
</ul>

twiddle.json

{
  "version": "0.15.1",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.js",
    "ember": "3.4.3",
    "ember-template-compiler": "3.4.3",
    "ember-testing": "3.4.3"
  },
  "addons": {
    "ember-data": "3.4.2"
  }
}