Did you know that jQuery has great support for Callbacks? Here are two ways you can tell if a function has completed running.

function runAlertNow () { 
  $(this).html('I just ran this function!');  
}

// both of these lines do the same thing  
$('#test').slideUp(400, runAlertNow);

$('#test').slideUp(400, function () {
  $(this).html('I just ran the anonymous function!');  
});