Reflect.js
function CreateMapPolyfill() {
            var cacheSentinel = {};
            var arraySentinel = [];
            var MapIterator = /** @class */ (function () {
                function MapIterator(keys, values, selector) {
                    this._index = 0;
                    this._keys = keys;
                    this._values = values;
                    this._selector = selector;
                }
                MapIterator.prototype["@@iterator"] = function () { return this; };
                MapIterator.prototype[iteratorSymbol] = function () { return this; };
                MapIterator.prototype.next = function () {
                    var index = this._index;
                    if (index >= 0 && index < this._keys.length) {
                        var result = this._selector(this._keys[index], this._values[index]);
                        if (index + 1 >= this._keys.length) {
                            this._index = -1;
                            this._keys = arraySentinel;
                            this._values = arraySentinel;
                        }
                        else {
                            this._index++;
                        }
                        return { value: result, done: false };
                    }
                    return { value: undefined, done: true };
                };
                MapIterator.prototype.throw = function (error) {
                    if (this._index >= 0) {
                        this._index = -1;
                        this._keys = arraySentinel;
                        this._values = arraySentinel;
                    }
                    throw error;
                };
                MapIterator.prototype.return = function (value) {
                    if (this._index >= 0) {
                        this._index = -1;
                        this._keys = arraySentinel;
                        this._values = arraySentinel;
                    }
                    return { value: value, done: true };
                };
                return MapIterator;
            }());
            return /** @class */ (function () {
                function Map() {
                    this._keys = [];
                    this._values = [];
                    this._cacheKey = cacheSentinel;
                    this._cacheIndex = -2;
                }
                Object.defineProperty(Map.prototype, "size", {
                    get: function () { return this._keys.length; },
                    enumerable: true,
                    configurable: true
                });
                Map.prototype.has = function (key) { return this._find(key, /*insert*/ false) >= 0; };
                Map.prototype.get = function (key) {
                    var index = this._find(key, /*insert*/ false);
                    return index >= 0 ? this._values[index] : undefined;
                };
                Map.prototype.set = function (key, value) {
                    var index = this._find(key, /*insert*/ true);
                    this._values[index] = value;
                    return this;
                };
                Map.prototype.delete = function (key) {
                    var index = this._find(key, /*insert*/ false);
                    if (index >= 0) {
                        var size = this._keys.length;
                        for (var i = index + 1; i < size; i++) {
                            this._keys[i - 1] = this._keys[i];
                            this._values[i - 1] = this._values[i];
                        }
                        this._keys.length--;
                        this._values.length--;
                        if (key === this._cacheKey) {
                            this._cacheKey = cacheSentinel;
                            this._cacheIndex = -2;
                        }
                        return true;
                    }
                    return false;
                };
                Map.prototype.clear = function () {
                    this._keys.length = 0;
                    this._values.length = 0;
                    this._cacheKey = cacheSentinel;
                    this._cacheIndex = -2;
                };
                Map.prototype.keys = function () { return new MapIterator(this._keys, this._values, getKey); };
                Map.prototype.values = function () { return new MapIterator(this._keys, this._values, getValue); };
                Map.prototype.entries = function () { return new MapIterator(this._keys, this._values, getEntry); };
                Map.prototype["@@iterator"] = function () { return this.entries(); };
                Map.prototype[iteratorSymbol] = function () { return this.entries(); };
                Map.prototype._find = function (key, insert) {
                    if (this._cacheKey !== key) {
                        this._cacheIndex = this._keys.indexOf(this._cacheKey = key);
                    }
                    if (this._cacheIndex < 0 && insert) {
                        this._cacheIndex = this._keys.length;
                        this._keys.push(key);
                        this._values.push(undefined);
                    }
                    return this._cacheIndex;
                };
                return Map;
            }());
            function getKey(key, _) {
                return key;
            }
            function getValue(_, value) {
                return value;
            }
            function getEntry(key, value) {
                return [key, value];
            }
        }
function CreateMapPolyfill() {
            var cacheSentinel = {};
            var arraySentinel = [];
            var MapIterator = /** @class */ (function () {
                function MapIterator(keys, values, selector) {
                    this._index = 0;
                    this._keys = keys;
                    this._values = values;
                    this._selector = selector;
                }
                MapIterator.prototype["@@iterator"] = function () { return this; };
                MapIterator.prototype[iteratorSymbol] = function () { return this; };
                MapIterator.prototype.next = function () {
                    var index = this._index;
                    if (index >= 0 && index < this._keys.length) {
                        var result = this._selector(this._keys[index], this._values[index]);
                        if (index + 1 >= this._keys.length) {
                            this._index = -1;
                            this._keys = arraySentinel;
                            this._values = arraySentinel;
                        }
                        else {
                            this._index++;
                        }
                        return { value: result, done: false };
                    }
                    return { value: undefined, done: true };
                };
                MapIterator.prototype.throw = function (error) {
                    if (this._index >= 0) {
                        this._index = -1;
                        this._keys = arraySentinel;
                        this._values = arraySentinel;
                    }
                    throw error;
                };
                MapIterator.prototype.return = function (value) {
                    if (this._index >= 0) {
                        this._index = -1;
                        this._keys = arraySentinel;
                        this._values = arraySentinel;
                    }
                    return { value: value, done: true };
                };
                return MapIterator;
            }());
            return /** @class */ (function () {
                function Map() {
                    this._keys = [];
                    this._values = [];
                    this._cacheKey = cacheSentinel;
                    this._cacheIndex = -2;
                }
                Object.defineProperty(Map.prototype, "size", {
                    get: function () { return this._keys.length; },
                    enumerable: true,
                    configurable: true
                });
                Map.prototype.has = function (key) { return this._find(key, /*insert*/ false) >= 0; };
                Map.prototype.get = function (key) {
                    var index = this._find(key, /*insert*/ false);
                    return index >= 0 ? this._values[index] : undefined;
                };
                Map.prototype.set = function (key, value) {
                    var index = this._find(key, /*insert*/ true);
                    this._values[index] = value;
                    return this;
                };
                Map.prototype.delete = function (key) {
                    var index = this._find(key, /*insert*/ false);
                    if (index >= 0) {
                        var size = this._keys.length;
                        for (var i = index + 1; i < size; i++) {
                            this._keys[i - 1] = this._keys[i];
                            this._values[i - 1] = this._values[i];
                        }
                        this._keys.length--;
                        this._values.length--;
                        if (key === this._cacheKey) {
                            this._cacheKey = cacheSentinel;
                            this._cacheIndex = -2;
                        }
                        return true;
                    }
                    return false;
                };
                Map.prototype.clear = function () {
                    this._keys.length = 0;
                    this._values.length = 0;
                    this._cacheKey = cacheSentinel;
                    this._cacheIndex = -2;
                };
                Map.prototype.keys = function () { return new MapIterator(this._keys, this._values, getKey); };
                Map.prototype.values = function () { return new MapIterator(this._keys, this._values, getValue); };
                Map.prototype.entries = function () { return new MapIterator(this._keys, this._values, getEntry); };
                Map.prototype["@@iterator"] = function () { return this.entries(); };
                Map.prototype[iteratorSymbol] = function () { return this.entries(); };
                Map.prototype._find = function (key, insert) {
                    if (this._cacheKey !== key) {
                        this._cacheIndex = this._keys.indexOf(this._cacheKey = key);
                    }
                    if (this._cacheIndex < 0 && insert) {
                        this._cacheIndex = this._keys.length;
                        this._keys.push(key);
                        this._values.push(undefined);
                    }
                    return this._cacheIndex;
                };
                return Map;
            }());
            function getKey(key, _) {
                return key;
            }
            function getValue(_, value) {
                return value;
            }
            function getEntry(key, value) {
                return [key, value];
            }
        }
naive Map shim