title: checkValidity() on part of a form?
body: <p>Is there a way to have <code>checkValidity()</code> only work on part of the form? For instance, checking validity on a <code>keyUp</code> event? Or is it strictly for complete form submission?</p>
  
  <p>If it doesn't work that way, is there any third party plugin that works as a shim for these kinds of cases?</p>
  
  <p>I haven't been able to find too much about <code>checkValidity()</code>...</p>