(...)Consider you have a function, and you wish to use in many classes. In practice, you create a class that contains your general-purpose methods, and then use it to augment other classes. Class with these general-purpose methods is called Mixin class. It is generally not instantiated or called directly, instead it exists to provide methods to other classes.'(...)
from : Chamnap Chhorn
http://chamnapchhorn.blogspot.com/2009/05/javascript-mixins.html
