Bug

controllers.application.js

import Ember from 'ember';

export default Ember.Controller.extend({
  appName: 'Ember Twiddle',
  oldLength: 0,
  tempValue: '',
  actions: {
    changeValue: function(e) {
      var input = e.target.value;
      input = input.replace(/[^\d\(\) -]/g, '');
			input = input.substr(0, 14);
			if (input.length < this.get('oldLength')) {
				switch (input.length) {
					case 0:
						this.set('tempValue', '');
						break;
					case 1:
						this.set('tempValue', '');
						break;
					case 6: 
						this.set('tempValue', input.substr(0,4));
						break;
					case 10:
						this.set('tempValue', input.substr(0,9));
						break;
					default:
						this.set('tempValue', input);
				}
			} else {
				switch (input.length) {
					case 0:
						this.set('tempValue', '');
						break;
					case 1:
						this.set('tempValue', '(' + input);
						break;
					case 4: this.set('tempValue', input + ') ');
							break;
					case 9: 
						this.set('tempValue', input + '-');
						break;
					case 15:
						this.set('tempValue', this.get('tempValue'));
						break;
					default:
						this.set('tempValue', input);
				}
			}
			this.set('oldLength', this.get('tempValue.length'));
    }
  }
});

templates.application.hbs

<h1>Welcome to {{appName}}</h1>
<br>
<br>
<input value={{tempValue}} oninput={{action "changeValue"}}>
{{tempValue}}
<br>
<br>

twiddle.json

{
  "version": "0.9.3",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/1.11.3/jquery.js",
    "ember": "2.6.0",
    "ember-data": "2.6.1",
    "ember-template-compiler": "2.6.0"
  }
}