Easily create data and accessor properties on any object...
Overview
The Util API provides a number of features that enable data and accessor properties to be created on any object with desired property descriptor flags.
object.addConst() – add a read-only, hidden, non-configurable data property to an object
object.addAccessor() – add a hudden, non-configurable accessor (getter/setter) property to an object
object.addProp() – add a property of any type with desired property descriptor to an object