tolower

controllers.application.js

import Ember from 'ember';

export default Ember.Controller.extend({
  appName: 'Ember Twiddle',
  
  actions: {
    toLower: function(value) {
    	this.set('athing', value.toLowerCase());
    }
  }
});

helpers.to-lower.js

import Ember from 'ember';

export function toLower(params/*, hash*/) {
  return params[0].toLowerCase();
}

export default Ember.Helper.helper(toLower);

templates.application.hbs

<h1>Welcome to {{appName}}</h1>
<br>
<br>
<h3>{{athing}}</h3>
<input value={{athing}} onInput={{action "toLower" value="target.value"}}>

{{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"
  }
}