https://stackoverflow.com/questions/45514999/ember-template-not-updating-when-array-in-model-is-modified

controllers.application.js

import Ember from 'ember';

export default Ember.Controller.extend({
  appName: 'Ember Twiddle',
  stuff:[2,3,4],
  actions:{
    insert(){
      this.get('stuff').unshiftObject(1);
    }
  }
});

templates.application.hbs

<h1 {{action 'insert'}}>Welcome to {{appName}}</h1>
<br>
{{#each stuff as | temp |}}
{{temp}}
{{/each}}
<br>
{{outlet}}
<br>
<br>

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"
  }
}