title: Regular expression for detecting round or square brackets
body: <p>I'm trying to find aiport codes given a string like <code>(JFK)</code> or <code>[FRA]</code> using a regular expression.</p>
  
  <p>I'm don't have to make sure if the mentioned airport code is correct. The braces can pretty much contain any three capital letters.</p>
  
  <p>Here's my current solution which does work for round brackets but not for square brackets:</p>
  
  <pre><code>[((\[]([A-Z]{{3}})[))\]]
  </code></pre>
  
  <p>Thanks!</p>