Classic Ember tracking on a POJO

controllers.application.js

import Ember from 'ember';

export default Ember.Controller.extend({
  appName: 'Ember Twiddle',
  
  foo: {
    bar: 'Baz' 
  },
  
  uppercaseFooBar: Ember.computed('foo.bar', function () {
    return this.foo.bar.toUpperCase();
  })
});

templates.application.hbs

<h1>foo.bar: {{foo.bar}}</h1>

<p>uppercaseFooBar: {{uppercaseFooBar}}</p>

{{input value=foo.bar}}

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"
  }
}