title: How to remove space, underscore from this regexp [^\w \xC0-\xFF]
body: <p>How to detect space, underscore is invalid? It has to be one word. But not working with</p>
  
  <p><code>[^\w \xC0-\xFF]</code></p>
  
  <ul>
  <li>if i do \w\xC0-\xFF i can detect the space</li>
  <li>but how do i detect the 'underscore' ?</li>
  </ul>
  
  <p>Inputs are invalid: <code>username1234 _1234</code> or <code>username 1234</code></p>