title: Delete duplicate elements from an array
body: <p>For example, I have an array like this;</p>
  
  <pre><code>var arr = [1, 2, 2, 3, 4, 5, 5, 5, 6, 7, 7, 8, 9, 10, 10]
  </code></pre>
  
  <p>My purpose is to discard repeating elements from array and get final array like this;</p>
  
  <pre><code>var arr = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
  </code></pre>
  
  <p>How can this be achieved in JavaScript?</p>
  
  <p>NOTE: array is not sorted, values can be arbitrary order.</p>