WeakMap is a collection introduced to JavaScript with EcmaScript 6. It
provides a mapping from objects to values, but allows any entry to be
garbage collected if the key is provably lost.
In order for it to be possible that a key is provably lost, weak maps
do not provide a way to access the key list.
This is a Node.js module that provides a shim and patcher for missing
or broken WeakMap implementations, suitable for use in Node.js and
browsers that provide the EcmaScript 5 property description interfaces.
