http://wiki.ecmascript.org/doku.php?id=harmony:simple_maps_and_sets

Map.js

/**
 * Specifications
 * http://wiki.ecmascript.org/doku.php?id=harmony:simple_maps_and_sets
 */

(function () {
	"use strict";
	
	/** A non-stupid alternative to Array.prototype.indexOf */
	function indexOfIdentical(keys, key) {
		var i;
		for (i = 0; i < keys.length; i += 1) {
			if (keys[i] === key) {
				return i;
			}
		}
		return -1;
	}
	
	var Map = window.Map = function (iterable) {
		var i;
		iterable = iterable || [];
		this.keysName = [];
		this.valsName = [];
		for (i = 0; i < iterable.length; i += 1) {
			this.set(iterable[i][0], iterable[i][1]);
		}
	};
	
	Map.prototype.get = function (key, defaultValue) {
		var i = indexOfIdentical(this.keysName, key);
		defaultValue = defaultValue || undefined;
		return i < 0 ? defaultValue : this.valsName[i];
	};
	
	Map.prototype.set = function (key, value) {
		var i = indexOfIdentical(this.keysName, key);
		if (i < 0) {
			i = this.keysName.length;
		}
		this.keysName[i] = key;
		this.valsName[i] = value;
	};
	
	Map.prototype.has = function (key) {
		return indexOfIdentical(this.keysName, key) >= 0;
	};
	
	Map.prototype.delete_ = function (key) {
		var i = indexOfIdentical(this.keysName, key);
		if (i < 0) {
			return false;
		}
		this.keysName.splice(i, 1);
		this.valsName.splice(i, 1);
		return true;
	};
	
	Map.prototype.clear = function () {
		this.keysName = [];
		this.valsName = [];
	};
	
	Map.prototype.items = function () {
		var i, array = [];
		for (i = 0; i < this.keysName.length; i += 1) {
			array.push([this.keysName[i], this.valsName[i]]);
		}
		return array;
	};
	
	Map.prototype.keys = function () {
		var i, array = [];
		for (i = 0; i < this.keysName.length; i += 1) {
			array.push(this.keysName[i]);
		}
		return array;
	};
	
	Map.prototype.values = function () {
		var i, array = [];
		for (i = 0; i < this.keysName.length; i += 1) {
			array.push(this.valsName[i]);
		}
		return array;
	};
	
	Object.defineProperty(Map.prototype, "iterator", {
		configurable: true,
		writable: true,
		value: Map.prototype.items
	});
}());

(function () {
	"use strict";
	var Set = window.Set = function (iterable) {
		var i;
		iterable = iterable || [];
		this.mapName = new window.Map();
		for (i = 0; i < iterable.length; i += 1) {
			this.add(iterable[i]);
		}
	};
	
	Set.prototype.add = function (key) {
		this.mapName.set(key, true);
	};
	
	Set.prototype.has = function (key) {
		return this.mapName.has(key);
	};
	
	Set.prototype.delete_ = function (key) {
		return this.mapName.delete_(key);
	};
	
	Set.prototype.values = function () {
		return this.mapName.keys();
	};
	
	Object.defineProperty(Set.prototype, "iterator", {
		configurable: true,
		writable: true,
		value: Set.prototype.values
	});
}());