JSFiddle - React, Tailwind, and code Playground

HTML

<script src="https://github.com/downloads/wycats/handlebars.js/handlebars-1.0.0.beta.6.js"></script>
<script src="https://github.com/downloads/emberjs/ember.js/ember-latest.js"></script>
<script type='text/x-handlebars' data-template-name='application'>

    {{view App.TopView}}

    {{outlet}}

    {{view App.BottomView}}
    
</script>

<script type='text/x-handlebars' data-template-name='top'>
    <p>This is the top view: {{section}}</p>
</script>

<script type='text/x-handlebars' data-template-name='bottom'>
    <p>This is the bottom view.</p>
</script>

<script type='text/x-handlebars' data-template-name='frontpage'>
    <p>This is the front page.</p>
</script>

JavaScript

var App = Em.Application.create();
  
  App.ApplicationController = Em.Controller.extend();
  
  App.TopController = Em.Controller.extend();
  
  App.BottomController = Em.Controller.extend();
  
  App.FrontpageController = Em.Controller.extend();

  App.ApplicationView = Em.View.extend({
    templateName: 'application',
    classNames: ['application']
  });

  App.TopView = Em.View.extend({
    templateName: 'top',

    sectionBinding: 'controller.section',
      
    classNames: ['top'],
    classNameBindings: ['section']
  });

  App.BottomView = Em.View.extend({
    templateName: 'bottom',
    classNames: ['bottom']
  });

  App.FrontpageView = Em.View.extend({
    templateName: 'frontpage',
    classNames: ['frontpage']
  });

  App.Router = Em.Router.extend({
    enableLogging: true,
    location: 'history',

    root: Em.Route.extend({

      goToFrontpage: Em.Route.transitionTo('frontpage'),

      index: Em.Route.extend({
        route: '/',
        redirectsTo: 'frontpage'
      }),

      frontpage: Em.Route.extend({
        route: '/',

        connectOutlets: function(router, context) {

          router.get('applicationController').connectOutlet({
            name: 'frontpage'
          });

          // THIS DOES WORK:
          router.set('applicationController.section', 'index');

        }
      })

    })

  });
  
  App.initialize();