Map.filter polyfill

poly.js

Object.defineProperty(Map.prototype, 'filter', {
    value: function (filterFunction) {
        const myMap = new Map();
        for (const [key, value] of this) {
            if (filterFunction(value, key, this)) {
                myMap.set(key, value);
            }
        }
        return myMap;
    }
});