title: Validate a JavaScript function name
body: <p>What would be a regular expression which I can use to match a valid JavaScript function name...</p>
  
  <p>E.g. <code>myfunction</code> would be valid but <code>my&lt;\fun\&gt;ction</code> would be invalid.</p>
  
  <pre><code>[a-zA-Z0-9_])?
  </code></pre>