JSFiddle - React, Tailwind, and code Playground

HTML

<script src="http://cloud.github.com/downloads/wycats/handlebars.js/handlebars-1.0.0.beta.6.js"></script>
<script src="http://cloud.github.com/downloads/emberjs/ember.js/ember-1.0.pre.js"></script>
<script type="text/x-handlebars" data-template-name="application">
  <p class="something" {{bindAttr class="isA:redbg:greenbg"}}>A {{isA}}</p>
  <p class="something" {{bindAttr class="isB:redbg:greenbg"}}>B {{isB}}</p>
  <a {{action "toggle" target="applicationController"}}>Click me to Toggle</a>
</script>

CSS

.redbg {
    background-color: red;
  }
  .greenbg {
    background-color: green;
  }

JavaScript

App = Ember.Application.create({
  VERSION: '0.0.0'
});

App.ApplicationController = Ember.Controller.extend({
  isA: true,
  isB: false
});

App.ApplicationView = Ember.View.extend({
  templateName: 'application',
  toggle: function() {
    this.controller.toggleProperty('isA');
    this.controller.toggleProperty('isB');
  }
});

App.Router = Ember.Router.extend({
  enableLogging: true,
  root: Ember.Route.extend({
    index: Ember.Route.extend({
      route: '/'
    })
  })
});

App.initialize();