Override Computed Properties

components.default-title.js

import Ember from 'ember';

const { computed, get, set } = Ember;

export default Ember.Component.extend({
  defaultTitle: 'Default Title',
  type: 'cool',
  title: computed('type', 'defaultTitle', {
    get() {
      const defaultTitle = get(this, 'defaultTitle');
      const type = get(this, 'type');

      if (type === 'cool') {
        return `Cool ${defaultTitle}`;
      }

      return defaultTitle;    
    }
  })
});

controllers.application.js

import Ember from 'ember';

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

templates.application.hbs

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

<h2>Default title</h2>
<p>{{default-title}}</p>

<h2>Default "cool" title</h2>
<p>{{default-title type="cool"}}</p>

<h2>Custom title</h2>
<p>{{default-title title="My Amazing Custom Title!"}}</p>

templates.components.default-title.hbs

<h3>{{title}}</h3>

twiddle.json

{
  "version": "0.10.6",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/1.11.3/jquery.js",
    "ember": "2.9.0",
    "ember-data": "2.9.0",
    "ember-template-compiler": "2.9.0",
    "ember-testing": "2.9.0"
  },
  "addons": {}
}