Tracked Builtins Demo

controllers.application\.js

import Controller from '@ember/controller';
import { action } from '@ember/object';
import { tracked } from 'tracked-built-ins';

export default class ApplicationController extends Controller {
  @tracked myArray = tracked([]);

  @action pushNum() {
    let num = Math.random();
  
    this.myArray.push(num);
  }
}

templates.application\.hbs

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

<button {{on 'click' this.pushNum}}>
  Add num
</button>

{{#each this.myArray as |num|}}
  {{num}}<br>
{{/each}}


<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",
    "tracked-built-ins": "1.0.2"
  }
}