WeakMap collection as specified in ECMAScript6. Roughly inspired by Mark Miller's and Kris Kowal's WeakMap implementation.

Differences are: - Assumes compliant ES5 environment (no weird ES3 workarounds or hacks) - Well modularized CJS style - Based on one solution.

Limitations - Will fail on non extensible objects provided as keys

Node.js is an event-based server-side JavaScript engine.