title: How to return "valid" if the input type="file" = file selected?
body: <p>I use jquery and the <a href="http://bassistance.de/jquery-plugins/jquery-plugin-validation/" rel="nofollow">jquery validate plugin</a> for my form.</p>
  
  <p>If the <code>input_17</code> has content <code>length &gt; 1</code>, it is required to select a file <code>input_1_67</code>. That works.</p>
  
  <pre><code>        input_17: {
          required: function(element) {
              return $("#input_1_67").val().length &gt; 1
          }
      }
  </code></pre>
  
  <p>Now, if the user has select a file i like to return a "valid" class to the <code>input_17</code>. Any ideas how i can get this class? And: i like to add this class only if </p>
  
  <pre><code>$("#input_1_67").val().length &gt; 1
  </code></pre>
  
  <p>and a file is select.</p>