title: Algorithm to tell if two arrays have identical members
body: <p>What's the best algorithm for comparing two arrays to see if they have the same members?</p>
  
  <p>Assume there are no duplicates, the members can be in any order, and that neither is sorted.</p>
  
  <pre><code>compare(
      [a, b, c, d],
      [b, a, d, c]
  ) ==&gt; true
  
  compare(
      [a, b, e],
      [a, b, c]
  ) ==&gt; false
  
  compare(
      [a, b, c],
      [a, b]
  ) ==&gt; false
  </code></pre>