title: express-validator isStrongPassword() function is not working
body: <p>I'm trying to do validation test by using express-validator.</p>
  <p>so far everything is working good except isStrongPassword()</p>
  <pre class="lang-js prettyprint-override"><code>import {check} from &quot;express-validator&quot;
  
  
  const val =   
      check('pwd')
          .exists()
          .withMessage('please enter the password')
          .isStrongPassword({minLength: 6})
          .withMessage('password is must be above six letters')
  
  Router.post('/signup',val,SignUp)
  
  
  const SignUp = async(req,res) =&gt; {
      // if email and password are invalid  throw the errors
      const errors = validationResult(req).array();
      if (errors &amp;&amp; errors.length) {
      console.log(errors);
      res.status(400).json({ errors });
  </code></pre>
  <p>my code is like that .but when I request password 1 letter or 7 letters regardless  It just call error. It seems to be doesn`t work
  anybody who knows why it happened? Thank you for your attention</p>