has-property-descriptors
Does the environment have full property descriptor support? Handles IE 8's broken defineProperty/gOPD.
define-data-property
Define a data property on an object. Will fall back to assignment in an engine without descriptors.
is-accessor-descriptor
Returns true if a value has the characteristics of a valid JavaScript accessor descriptor.
is-data-descriptor
Returns true if a value has the characteristics of a valid JavaScript data descriptor.