title: Yii2 validation with XRegExp, \p{L} not working
body: <p>I'm using Yii2 framework and I have a <code>Validator</code> that should do client-side validation. I have a regex that looks like this: <code>/^[\\p{L}]+$/u</code> for simplicity, but my actual regex is a bit more complicated, but the \p{L} part is what causes the problems.</p>
  
  <p>And so my code like this in the validator class:</p>
  
  <pre><code>public function clientValidateAttribute($model, $attribute, $view)
  {
      $message = json_encode($this-&gt;message, JSON_UNESCAPED_SLASHES | JSON_UNESCAPED_UNICODE);
      return &lt;&lt;&lt;JS
      if (!XRegExp('/^[\\p{L}]+$/u').test(value)) {
          messages.push($message);
      }
  JS;
  }
  </code></pre>
  
  <p>Problem is, this always fails for \p{L} but if I change the pattern for something like /^[A-Z]+$/ it works flawlessly.</p>
  
  <p>I'm using the 1.3.0 xregexp-all.js. It is added to in an <code>AssetBundle</code> class in \assets\AppAsset.php</p>