steps

controllers.application.js

import Ember from 'ember';

export default Ember.Controller.extend({
  appName: 'Ember Twiddle',
  totalSteps: 5,
  currentStep: 2,
  
  stepsArray: Ember.computed('totalSteps', 'currentStep', function() {
    const totalSteps = this.get('totalSteps');
    const currentStep = this.get('currentStep');
    
    return [...Array(totalSteps)].map((_, i) => {
      
      return {
       completed: i < currentStep 
      }
    })
  })
});

templates.application.hbs

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

<ul>
	{{#each stepsArray as |step|}}
		<li>Step is {{if step.completed 'done' 'is not done'}}</li>
  {{/each}}
</ul>

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"
  }
}