Rather than declaring empty anonymous functions all around, introduce and use a single empty function. Thanks to Matt Kruse for the suggestion.

src/ajax.js

@@ -384,7 +384,7 @@ jQuery.extend({
 			// The request was aborted, clear the interval and decrement jQuery.active
 			if ( !xhr || xhr.readyState === 0 ) {
 				requestDone = true;
-				xhr.onreadystatechange = function(){};
+				xhr.onreadystatechange = jQuery.noop;
 
 				// Handle the global AJAX counter
 				if ( s.global && ! --jQuery.active ) {
@@ -394,7 +394,7 @@ jQuery.extend({
 			// The transfer is complete and the data is available, or the request timed out
 			} else if ( !requestDone && xhr && (xhr.readyState === 4 || isTimeout === "timeout") ) {
 				requestDone = true;
-				xhr.onreadystatechange = function(){};
+				xhr.onreadystatechange = jQuery.noop;
 
 				status = isTimeout === "timeout" ?
 					"timeout" :

src/core.js

@@ -464,6 +464,8 @@ jQuery.extend({
 		return true;
 	},
 
+	noop: function() {},
+
 	// Evalulates a script in a global context
 	globalEval: function( data ) {
 		if ( data && rnotwhite.test(data) ) {

src/event.js

@@ -427,7 +427,7 @@ jQuery.event = {
 		ready: {
 			// Make sure the ready event is setup
 			setup: jQuery.bindReady,
-			teardown: function() {}
+			teardown: jQuery.noop
 		},
 
 		live: {

src/offset.js

@@ -121,7 +121,7 @@ jQuery.offset = {
 
 		body.removeChild( container );
 		body = container = innerDiv = checkDiv = table = td = null;
-		jQuery.offset.initialize = function() {};
+		jQuery.offset.initialize = jQuery.noop;
 	},
 
 	bodyOffset: function( body ) {