Char counter

components.char-counter.js

import Ember from 'ember';

const MAX_VALUE = 10;

export default Ember.Component.extend({
  value: 0,
  
  showWarning: Ember.computed.gt('value', MAX_VALUE),
  
  actions: {
    onValueChanged(e) {
      this.set('value', e.target.value.length);
    }
  }
});

controllers.application.js

import Ember from 'ember';

export default Ember.Controller.extend({
  appName: 'Ember Twiddle'
});

styles.app.css

body {
  margin: 12px 16px;
  font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif;
  font-size: 12pt;
}

.fucked {
  color: red;
}

templates.application.hbs

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

{{#char-counter as |props|}}
	{{textarea input=props.onValueChanged}}
  {{#if props.showWarning}}
  <div>Ruh roh!</div>
  {{/if}}
{{/char-counter}}

{{#char-counter as |props|}}
	{{textarea input=props.onValueChanged}}
  {{#if props.showWarning}}
  <div class="fucked">I fucked up!</div>
  {{/if}}
{{/char-counter}}
<br>
<br>

templates.components.char-counter.hbs

{{yield
	(hash 
  	onValueChanged=(action 'onValueChanged')
    showWarning=showWarning
  )
}}

<div class="count">{{value}}</div>

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"
  }
}