title: jQuery Validate: Validate that one field, or both fields of a pair are required
body: <p>I have a form that I am trying to validate that has two fields:</p>
  
  <pre><code>&lt;div class="entryForm"&gt;
      &lt;div class="formField"&gt;
          &lt;label for="fieldEmailAddress"&gt;Email address:&lt;/label&gt;
          &lt;input type="email" name="fieldEmailAddress" id="fieldEmailAddress"/&gt;
      &lt;/div&gt;
      &lt;div class="formField"&gt;
          &lt;label for="fieldMobileNumber"&gt;Mobile number:&lt;/label&gt;
          &lt;input type="text" name="fieldMobileNumber" id="fieldMobileNumber"/&gt;
      &lt;/div&gt;
  &lt;/div&gt;
  </code></pre>
  
  <p>Here's my jQuery Validation wireup:</p>
  
  <pre><code>&lt;script type="text/javascript"&gt;
      $(document).ready(function () {
          $('#form1').validate({ rules: { fieldMobileNumber: { phoneUS: true } } });
      });
  &lt;/script&gt;
  </code></pre>
  
  <p><strong>What I'd like to do is add an additional validation rule that says: <em>the form is not valid if both fieldEmailAddress and fieldMobileNumber are blank.</em></strong>  In other words, I'd like to make it such that at least one of either fieldEmailAddress or fieldMobileNumber is required. It seems like most of the jQuery Validation custom methods are designed to only work for one field at a time - I need to validate both.</p>
  
  <p>Any ideas?</p>