New Twiddle

application.controller.js

import Ember from 'ember';

export default Ember.Controller.extend({
  appName:'Ember Twiddle',
  
  actions: {
    addExpense() { this.get('expense').pushObject(Ember.Object.create({amount: 100}));
    }
  },
  
  expense: Ember.computed(function() {
    return Ember.A([
      Ember.Object.create({amount: 100}),
      Ember.Object.create({amount: 100})
    ]);
  }),
  
  totalExpenses:  Ember.computed('expense.@each.amount', function() {
    return this.get('expense').reduce(function (sum, exp) {
      return sum + exp.amount;
    }, 0);
  })
  
});

application.template.hbs

<h1>Welcome to {{appName}}</h1>
<br>
<br>
<ul>
{{#each expense as |exp|}}
  <li>{{exp.amount}}</li>
{{/each}}
</ul>
<b>Total: </b>{{totalExpenses}}
<br>
<br>
{{input type="button" click=(action "addExpense") value="Add 100"}}
<br>
{{outlet}}
<br>
<br>

twiddle.json

{
  "version": "0.4.17",
  "EmberENV": {
    "FEATURES": {}
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/1.11.3/jquery.js",
    "ember": "https://cdnjs.cloudflare.com/ajax/libs/ember.js/2.2.0/ember.debug.js",
    "ember-data": "https://cdnjs.cloudflare.com/ajax/libs/ember-data.js/2.2.0/ember-data.js",
    "ember-template-compiler": "https://cdnjs.cloudflare.com/ajax/libs/ember.js/2.2.0/ember-template-compiler.js"
  }
}