In jQuery.event.trigger:

if ( jQuery.isFunction( jQuery.data(elem, "handle") ) )

val = jQuery.data(elem, "handle").apply( elem, data );

Problem 1:

That's 2 calls to jQuery.data and one possibly useless call to

jQuery.isFunction.

Problem 2:

Is it really necessary to check if jQuery.data(elem, "handle") is a function ? what else could it be?

Proposed change:

var handle = jQuery.data(elem, "handle");

if(handle) val = handle.apply( elem, data );