New Twiddle

components.text-area.js

import Ember from 'ember';

const MAX_ROWS = 10;
export default Ember.TextArea.extend({
  rows: Ember.computed('value', function() {
  return Math.min(this.getWithDefault('value', '').split(/\r*\n/).length, MAX_ROWS);
})
});

controllers.application.js

import Ember from 'ember';

export default Ember.Controller.extend({
  appName: 'Ember Twiddle',
  
  textAreaValue: 'hello paul',
  
  actions: {
    clearText() {
      this.set('textAreaValue', '');
    }
  }
});

templates.application.hbs

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

{{text-area value=textAreaValue}}<br />

<button {{action "clearText"}}>Clear</button>
<br>
<br>

twiddle.json

{
  "version": "0.10.4",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/1.11.3/jquery.js",
    "ember": "2.7.0",
    "ember-data": "2.7.0",
    "ember-template-compiler": "2.7.0"
  },
  "addons": {}
}