define-properties
Define multiple non-enumerable properties at once. Uses `Object.defineProperty` when available; falls back to standard assignment in older engines.
gopd
`Object.getOwnPropertyDescriptor`, but accounts for IE's broken implementation.
is-descriptor
Returns true if a value has the characteristics of a valid JavaScript descriptor. Works for data descriptors and accessor descriptors.
is-data-descriptor
Returns true if a value has the characteristics of a valid JavaScript data descriptor.
is-accessor-descriptor
Returns true if a value has the characteristics of a valid JavaScript accessor descriptor.