title: Counting common elements in arrays
body: <p>I have two objects:</p>
  <pre class="lang-json prettyprint-override"><code>obj1 [
   'Anime',
   'Movies/TV Series',
   'Coding',
   'Cooking',
   'Sport/Fitness',
   'Gaming'
  ]
  </code></pre>
  <p>and</p>
  <pre class="lang-json prettyprint-override"><code>obj 2 [
   'Music',
   'Movies/TV Series',
   'Coding',
   'Party/Night Clubs',
   'Gaming',
   'Traveling',
   'Roleplay'
  ]
  </code></pre>
  <p>I need to count the number of common elements in arrays.
  How can I do it in <code>javascript</code>?</p>
  <p>Thanks for help in advance!</p>