The global window namespace.
A function that allows you to instantiate an object from a string representation of it.
str:The fully-qualified name of the constructor function to instantiate, e.g. "jStage.Actor".
An instantiated object, or null.
A polyfill that uses IE's ActiveXObject("MsXml2.XmlHttp") in cases where window.XMLHttpRequest does not exist.
An object that may be used to perform AJAX operations.
The famous requestAnimationFrame polyfill that's floating around the internet in a million different forms, by Erik Möller, Paul Irish, Tino Zijdel, Tim Hall, and others.
callback:A parameter specifying a function to call when it's time to update your animation for the next repaint. The callback has one single argument, a DOMHighResTimeStamp, which indicates the current time for when requestAnimationFrame starts to fire callbacks.
childFn:The function that will be the 'subclass'.
parentFn:The function that the 'subclass' is inheriting from.