New Twiddle

controllers.application.js

import Ember from 'ember';

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

helpers.fragment.js

import Ember from 'ember';

export default Ember.Helper.extend({
  init() {
    this._super(...arguments);
    this.set('i', 0);
    this.tick();
  },
  
  tick() {
    this.incrementProperty('i');
    this.recompute();
    Ember.run.later(() => this.tick(), 1000);
  },
    
  compute() {    
    let { i } = this;

    let fragment = document.createDocumentFragment();

    let div1 = document.createElement('div');
    let text1 = document.createTextNode(`div1.${i}!`);
    div1.appendChild(text1);
    fragment.appendChild(div1);

    let div2 = document.createElement('div');
    let text2 = document.createTextNode(`div2.${i}!`);
    div2.appendChild(text2);
    fragment.appendChild(div2);

    return fragment;
  }
});

templates.application.hbs

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

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"
  }
}