New Twiddle

controllers.application.js

import Ember from 'ember';

const { computed, Controller, get, isNone, set } = Ember;

const describe = (value) =>
  isNone(value)
  ? '`undefined` or `null`'
  : value === ''
    ? '<empty string>'
    : value;

export default Controller.extend({
  appName: 'Ember Twiddle',
  
  theSubmittedValue: undefined,
  theValue: undefined,
  
  descriptiveValue: computed('theValue', function() {
    const theValue = get(this, 'theValue');
    return describe(theValue);
  }),
  
  descriptiveSubmitted: computed('theSubmittedValue', function() {
    return describe(get(this, 'theSubmittedValue'));
  }),
  
  actions: {
    setValue(value = '') {
      return set(this, 'theSubmittedValue', value);
    },
  }
});

templates.application.hbs

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

<form {{action 'setValue' theValue on='submit'}}>
<input value={{theValue}} onchange={{action (mut theValue) value='target.value'}}>
<button type='submit' onclick={{action 'setValue' theValue}}>submit!</button>
</form>
<p><code>theValue</code> is {{descriptiveValue}}</p>
<p><code>theSubmittedValue</code> is {{descriptiveSubmitted}}</p>

twiddle.json

{
  "version": "0.11.0",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/1.11.3/jquery.js",
    "ember": "2.10.2",
    "ember-data": "2.11.0",
    "ember-template-compiler": "2.10.2",
    "ember-testing": "2.10.2"
  },
  "addons": {}
}