New Twiddle

components.x-button.js

import Ember from 'ember';

const {
  computed,
  get
} = Ember;

export default Ember.Component.extend({
  tagName: 'button',
  classNames: [
    'ba',
    'white',
    'input-reset',
    'link',
    'ph3',
    'pv2'
  ],
  classNameBindings: [
    'styleClass'
  ],
  
  style: null,
  styleClass: computed('style', function() {
		let style = get(this, 'style');
    let classes = [];
    console.log('style', style);
    if (style === 'primary') {
      classes.push('bg-red');
      classes.push('b--red');
    } else {
      classes = ['b--green', 'bg-green'];
    }
    return classes.join(' ');
  })
});

controllers.application.js

import Ember from 'ember';

export default Ember.Controller.extend({
});

templates.application.hbs

<link rel="stylesheet" href="https://unpkg.com/[email protected]/css/tachyons.min.css"/>

{{#x-button}}hello{{/x-button}}
{{#x-button style="primary"}}hello{{/x-button}}

templates.components.x-button.hbs

{{yield}}

twiddle.json

{
  "version": "0.10.5",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/1.11.3/jquery.js",
    "ember": "2.8.0",
    "ember-data": "2.8.0",
    "ember-template-compiler": "2.8.0",
    "ember-testing": "2.8.0"
  },
  "addons": {}
}