class-utils
Utils for working with JavaScript classes and prototype methods.
delegate-properties
Deep-clone properties from one object to another and make them non-enumerable, or make existing properties on an object non-enumerable.
java-class
Class.js is a Javascript library designed to allow easy, non-obtrusive creation of Java-like classes without requiring a cross-compiler, and without otherwise interfering with the capabilities of Javascript.
extend-this
An extensible framework for defining "recipes" for extending an object using properties from other objects.