title: ExpressJS route regex: how to match a param to everything except one route
body: <p>I have a route defined something like this to catch <code>code</code> param:</p>
  
  <pre><code>app.get('/:code([a-zA-Z]{3})', codeHandler);
  </code></pre>
  
  <p>It matches all codes which are three letter long, and it is working fine. But I want to change  it to match every code except one. For example, lets say I want to exclude "cct". I tried using negative lookahead to excude "cct" from route by
  modifying the above matcher like so:</p>
  
  <pre><code>app.get('/:code((?!cct)[a-zA-Z]{3})', codeHandler);
  </code></pre>
  
  <p>But now this route doesnt match anything. Even valid codes that used to be caught earlier are now not matching. I dont know what I am doing wrong.</p>