Eng Example

controllers.application.js

import Ember from 'ember';

const { $ } = Ember;

export default Ember.Controller.extend({
  valueToEncode: null,
  encodedValue: '- - - - - ',
  
  valueToDecode: null,
  decodedValue: '- - - - -',
  
  actions: {
    encode() {
      const word = this.get('valueToEncode');
      const t = word.replace(/\w/g, function(c) {
        const i = 'abcdefghijklmnopqrstuvwxyz'.indexOf(c);
        return 'abcdefghijklmnopqrstuvwxyz'[(i + 4) % 26];
      });
      this.set('encodedValue', t);
    },
    
    decode() {
      const word = this.get('valueToDecode');
      const t = word.replace(/\w/g, function(c) {
        const i = 'abcdefghijklmnopqrstuvwxyz'.indexOf(c);
        return 'abcdefghijklmnopqrstuvwxyz'[(i % 26) - 4];
      });
      this.set('decodedValue', t);
    }
  }
});

styles.app.css

body {
  text-align: center;
}

div {
  font-size: 60px;
}

button {
  font-size: 24px;
}

templates.application.hbs

{{input 
  value=valueToEncode 
  enter=(action "encode")
}}
<button {{action "encode"}}>Encode</button>
<div>{{encodedValue}}</div>

<hr>

{{input 
	value=valueToDecode 
  enter=(action "decode")
}}
<button {{action "decode"}}>Decode</button>
<div>{{decodedValue}}</div>

twiddle.json

{
  "version": "0.15.1",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.js",
    "ember": "3.4.3",
    "ember-template-compiler": "3.4.3",
    "ember-testing": "3.4.3"
  },
  "addons": {
    "ember-data": "3.4.2"
  }
}