New Twiddle

controllers.application\.js

import Controller from '@ember/controller';
import { tracked } from "@glimmer/tracking";

class StorageModel {
  @tracked foo = "1";

  get bar() { return 2; }

  toJSON() {
    const keys = Object.keys(this);
    const protoKeys = Object.keys(this.__proto__);
    console.log({ keys, protoKeys });
  }
}

export default class ApplicationController extends Controller {
  appName = 'Ember Twiddle';
	data = new StorageModel();
  constructor(...args) {
    super(...args);
    this.data.toJSON();
    console.log(this.data);
  }
}

templates.application\.hbs

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

twiddle\.json

{
  "version": "0.17.1",
  "EmberENV": {
    "FEATURES": {},
    "_TEMPLATE_ONLY_GLIMMER_COMPONENTS": false,
    "_APPLICATION_TEMPLATE_WRAPPER": true,
    "_JQUERY_INTEGRATION": true
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/3.5.1/jquery.js",
    "ember": "3.18.1",
    "ember-template-compiler": "3.18.1",
    "ember-testing": "3.18.1"
  },
  "addons": {
    "@glimmer/component": "1.0.0"
  }
}