Added some tweaks to $.type to handle null and undefined. Added a bunch of unit tests as well.

src/core.js

@@ -446,7 +446,11 @@ jQuery.extend({
 	},
 
 	type: function( obj ) {
-		return toString.call(obj).slice(8, -1).toLowerCase();
+		return obj === null ?
+			"null" :
+			obj === undefined ?
+			"undefined" :
+			toString.call(obj).slice(8, -1).toLowerCase();
 	},
 
 	isPlainObject: function( obj ) {