title: Finding what is common to two arrays
body: <p>Is there a way to compare two arrays and show what is common to both of them?</p>
  
  <pre><code>array1 = ["pig", "dog", "cat"]
  array2 = ["dog", "cat", "pig", "horse"]
  </code></pre>
  
  <p>What do I type to show that <code>["pig", "dog", "cat"]</code> are common between these two arrays?</p>