ljharbside-channel-map 
Store information about any JS value in a side channel, using a Map.
Warning: if the key is an object, this implementation will leak memory until you delete it.
Use side-channel for the best available strategy.
Getting started
npm install --save side-channel-mapUsage/Examples
const assert = require('assert');
const getSideChannelMap = require('side-channel-map');
const channel = getSideChannelMap();
const key = {};
assert.equal(channel.has(key), false);
assert.throws(() => channel.assert(key), TypeError);
channel.set(key, 42);
channel.assert(key); // does not throw
assert.equal(channel.has(key), true);
assert.equal(channel.get(key), 42);
channel.delete(key);
assert.equal(channel.has(key), false);
assert.throws(() => channel.assert(key), TypeError);Tests
Clone the repo, npm install, and run npm test