Union Arrays

controllers.application.js

import Ember from 'ember';

export default Ember.Controller.extend({
  appName: 'Ember Twiddle',
  
  lettersArray: ['A', 'B', 'B', 'C'],
  uniqLettersArray: ['A', 'B', 'C'],
  unionedLettersArray: Ember.computed.union('lettersArray', 'uniqLettersArray'),
  
  playerLetters: 'ABBC',
  
  duplicates: Ember.computed('playerLetters', function() {
  	let letterArray = Ember.A(Ember.get(this, 'playerLetters').split(''));
    let uniqueLetterArray = letterArray.uniq();
    if (Ember.get(letterArray, 'length') !== Ember.get(uniqueLetterArray, 'length')) {
        let dupeLetters = letterArray.reject(item => {
            return uniqueLetterArray.includes(item);
        });
				
        return dupeLetters;
    } else {
      return null;                             
    }
  })
});

templates.application.hbs

<h1>Welcome to {{appName}}</h1>
{{!--
<br>
<br>
Player Letters: {{#each lettersArray as |letter|}} {{letter}} {{/each}}
<br>
<br>
Unique Letters: {{#each uniqLettersArray as |letter|}} {{letter}} {{/each}}
<br>
<br>
Unioned Letters: {{#each unionedLettersArray as |letter|}} {{letter}} {{/each}}
<br>
<br>
--}}
<br>
{{log duplicates}}
Duplicates: {{#each duplicates as |letter|}} {{letter}} {{/each}}

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"
  }
}