title: Javascript ECMAScript 5: arrays merging and deduction
body: <p><strong>I have</strong> got 3 arrays:</p>
  
  <pre><code>presentEntities = ['1', '2', '3'];
  addedEntities = ['3', '4'];
  removedEntities = ['2'];
  </code></pre>
  
  <p><strong>I need:</strong></p>
  
  <ol>
  <li>Merge <code>presentEntities</code> with <code>addedEntities</code> and take into account possible duplicates (means I need a Set)</li>
  <li>Deduct <code>removedEntities</code> from the result</li>
  </ol>
  
  <p><strong>Expected result:</strong></p>
  
  <pre><code>['1', '3', '4']
  </code></pre>
  
  <p><strong>Question:</strong> was is the true way to do that in javascript?</p>