interpolate

components.my-btn.js

import Ember from 'ember';

const REGEX_GET_DEPS = /[^[\]]+(?=])/g;
const REGEX_REPLACE = /\[(\w+)\]/g;
const DELETE_SYMBOL = '$$DELETE$$';

const interpolate = (text) => {
  const deps = text.match(REGEX_GET_DEPS);
  
  return Ember.computed(...deps, function(){
  	const props = Ember.getProperties(this, ...deps);

    return text
     .replace(REGEX_REPLACE, (_,key) => props[key] || DELETE_SYMBOL )
     .split(' ')
     .filter(cls => !cls.includes(DELETE_SYMBOL))
     .join(' ');
  })
};


export default Ember.Component.extend({
  classNameBindings: ['klass'],
  klass: interpolate('c-btn c-btn--[type] c-btn--[size]')
});

controllers.application.js

import Ember from 'ember';

export default Ember.Controller.extend({
  appName: 'Ember Twiddle'
});

templates.application.hbs

<h1>Welcome to {{appName}}</h1>
<br>
<br>
{{outlet}}
<br>
<br>

{{my-btn size="s" }}

{{my-btn type="primary" size="xl"}}

templates.components.my-btn.hbs

{{yield}}
Klass :: {{klass}}

twiddle.json

{
  "version": "0.12.1",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/1.11.3/jquery.js",
    "ember": "2.12.0",
    "ember-template-compiler": "2.12.0",
    "ember-testing": "2.12.0"
  },
  "addons": {
    "ember-data": "2.12.1"
  }
}