get event.target in focusin binding function

I am fixing a problem in jQuery.Validator.js. I have to get the current
input in the 'onfocusin'.

It seems that the "event.target" is what I needed.

But how can I get the event object in the follwing binding function?

<code>
$.extend($.validator, {
  defaults: {
          ......
  onfocusin: function(element) {
              // how to get event.target here?
              ......
        }
        }

</code>

Thanks!
Arthur