title: How can I invert a regular expression in JavaScript?
body: <p>I have a string A and want to test if another string B is not part of it. This is a very 
  simple regex whose result can be inverted afterwards.</p>
  
  <p>I could do:</p>
  
  <pre><code>/foobar/.test('foobar@bar.de')
  </code></pre>
  
  <p>and invert it afterwards, like this:</p>
  
  <pre><code>!(/foobar/).test('foobar@bar.de') 
  </code></pre>
  
  <p>The problem I have is, that I need to do it within the regular expression and not with their result. Something like:</p>
  
  <pre><code>/!foobar/.test('foobar@bar.de')
  </code></pre>
  
  <p>(which does not work)</p>
  
  <p>In other words: the regular expression should test for a non-existence and return true in that case.</p>
  
  <p>Is this possible with JavaScript?</p>