title: Regex: Invalid group specifier name - react native
body: <p>My regex works in browser but shows an error in react-native expo app (android) development </p>
  
  <p>Regex:</p>
  
  <pre><code>/^(?=.{0,20}$)(?![_.0-9])(?!.*[_.]{2})[a-zA-Z0-9._]+(?&lt;![_.])$/
  </code></pre>
  
  <p>error:</p>
  
  <pre><code>Invalid regular expression: invalid group specifier name
  no stack
  </code></pre>
  
  <p>How to fix this error, thanks </p>