Example of using router service

controllers.application.js

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

export default Ember.Controller.extend({
  appName: 'Ember Twiddle',

  router: service(),

  // In a real app with a more complex nav panel, I would probably 
  // put this logic in its own service so I don't overcomplicate
  // the application controller.
  showNavButton: computed('router.currentRouteName', function() {
    return(this.get('router.currentRouteName') === 'index');
  })
});

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('home')
});

export default Router;

templates.application.hbs

<h1>Welcome to {{appName}}</h1>
<br>
<br>
<div class="nav-bar">
  <p>{{#link-to "index"}}index{{/link-to}}</p>
  <p>{{#link-to "home"}}home{{/link-to}}</p>
  <p>current route name is: {{router.currentRouteName}}</p>
  {{#if showNavButton}}
    <button>Click Me</button> This button is only visible if on index route
  {{/if}}
</div>

{{outlet}}
<br>
<br>

twiddle.json

{
  "version": "0.15.0",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.js",
    "ember": "3.2.2",
    "ember-template-compiler": "3.2.2",
    "ember-testing": "3.2.2"
  },
  "addons": {
    "ember-data": "3.2.0"
  }
}