New Twiddle

controllers.application.js

import Ember from 'ember';
import { computed } from '@ember/object';
import { inject as service } from '@ember/service';

export default Ember.Controller.extend({
  router: service(),

  currentURL: computed('router.currentURL', function() {
    return this.router.currentURL;
  }),
});

router.js

import EmberRouter from '@ember/routing/router';
import config from './config/environment';

const Router = EmberRouter.extend({
  location: 'none',
  rootURL: config.rootURL
});

Router.map(function() {
  this.route('my-route');
  this.route('my-routeA', function() {
    this.route('my-sub-route');
  });
});



export default Router;

routes.my-route.js

import Ember from 'ember';
import { inject as service } from '@ember/service';

export default Ember.Route.extend({
  router: service(),
  
  // navigatee to my-routeA or my-sub-route, and then back to
  // my-route, and you'll see the previousURL
  setupController() {
    console.log('previous URL:', this.router.currentURL);
  }
});

templates.application.hbs

<h1>Getting URL from the router service</h1>
<br>
<br>
{{outlet}}

currentURL: {{this.currentURL}}

<br>
<br>

{{#link-to 'my-route'}}
  my-route
{{/link-to}}
|
{{#link-to 'my-routeA'}}
  my-routeA
{{/link-to}}
|
{{#link-to 'my-routeA.my-sub-route'}}
  my-sub-route
{{/link-to}}

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"
  }
}