RSVP

controllers.application.js

import Ember from 'ember';

export default Ember.Controller.extend({
  appName: 'Ember Twiddle',
  
  actions: {
    aacc() {
      return Ember.RSVP.Promise.resolve().then((resolve) => {
        console.log('final');
        Ember.RSVP.Promise.resolve().then((resolve) => {
           console.log('in bet');
        }).finally(() => {
  	      console.log('in bet 1');
	      });
      }).finally(() => {
        console.log('final 1');
      });
    }
  }
});

templates.application.hbs

<h1 {{action "aacc"}}>Welcome to {{appName}}</h1>
<br>
<br>
{{outlet}}div
<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"
  }
}