Jquery trigger another keyup event

Question

I have keypress function and I want to fire tab Key event on pressing Up Arrow and Down Arrow key press something like this:

   if (evt.keyCode == 38) {
        evt.preventDefault();
        jQuery.event.trigger({ type: 'keyup', which: 9 });
    }
    if (evt.keyCode == 40) {
        evt.preventDefault();
        jQuery.event.trigger({ type: 'keyup', which: 9 });
    }