title: add class to input field if name is x
body: <p>In my website load a js file from commercial service, so I don't have possibility to customize this file, the output of this is a form with various input field, every field have the same class name "wf-input", now I want add to a specific field a jquery date picker but don't have a class for select only a one field.</p>
  
  <p>This is a field I want add a datepicker</p>
  
  <pre><code>&lt;input type="text" name="x4" class="wf-input"&gt;
  </code></pre>
  
  <p>Now my request is how add a class name to only this field?</p>
  
  <p>The only difference between field is (name="x4).</p>
  
  <p>The code for initializing datepicker is this:</p>
  
  <pre><code>$(function() {
      $( ".x4picker" ).datepicker();
    });
  </code></pre>
  
  <p>How make this work with javascript??</p>