Constructor Pattern? or do you mean how objects are created through Constructors?
getOwnPropertyDescriptor() is somewhat easier. in ECMAScript 262 edition 5, there were property descriptors introduced, which allow a certain amount of property configuration (e.g. property is not writeable). see also https://developer.mozilla.org/en-US/...defineProperty
. getOwnPropertyDescriptor() just gives you access to those descriptors.