An ESnext spec-compliant Map shim/polyfill/replacement that works as far down as ES3.

This package implements the es-shim API interface. It works in an ES3-supported environment and complies with the spec.

npm install --save es-map

var map = new Map();
var obj = {};

map.set(1, 2).set(obj, 4);

map.get(obj); // 4
map.has(3); // false

Simply clone the repo, npm install, and run npm test