New Twiddle

controllers.application.js

import Ember from 'ember';

export default Ember.Controller.extend({
  actions: {
    activate(name) {
      if(this.currentTab === name) {
        this.set('currentTab', '');
      } else {
        this.set('currentTab', name);
      }
    }
  }
});

templates.application.hbs

<ul>
  <li role="button" onclick={{action 'activate' 'tab1'}}>Tab1</li>
  <li role="button" onclick={{action 'activate' 'tab2'}}>Tab2</li>
</ul>

{{#if (eq currentTab 'tab1')}}
	<div>
    Tab 1
  </div>
{{/if}}

{{#if (eq currentTab 'tab2')}}
	<div>
    Tab 2
  </div>
{{/if}}

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",
    "ember-truth-helpers": "2.1.0"
  }
}