area51/lib/es6/symbol.js

Experimental prototypes of alien things built in JavaScript. The bits may end up living in a different package.

"use strict";

Object.defineProperty(exports, "__esModule", {
	value: true
});

if (typeof Symbol === "undefined") {

	var idx = 0,
	    global = [],
	    cache = {},
	    map = {};

	var Symbol = function Symbol(description) {
		if (!(this instanceof Symbol)) {
			return new Symbol(description, arguments[1] || null);
		}

		this.description = description;

		var id = description;
		if (!id || id[0] !== "@") id = (idx++).toString() + (id || "");

		if (arguments[1] && arguments[1] === true) {
			global.push(description || id);
			map[description || id] = id;
		}

		this.id = id;
		cache[id] = this;

		Object.defineProperty(Object.prototype, id, {
			set: function set(value) {
				Object.defineProperty(this, id, {
					value: value,
					enumerable: false,
					writable: true
				});
			}
		});
	};

	Symbol.prototype = {
		toString: function toString() {
			return this.id;
		}
	};

	Symbol["for"] = function (key) {
		var symbol;

		if (global.indexOf(key) > -1) symbol = cache[map[key]];

		if (!symbol) symbol = Symbol(key, true);

		return symbol;
	};

	Symbol.keyFor = function (symbol) {
		return symbol.description;
	};

	Symbol.iterator = Symbol("@@iterator");

	Object.getOwnPropertySymbols = function (object) {
		var symbols = [];

		for (var prop in cache) {
			if (object[cache[prop]] !== undefined) symbols[symbols.length] = cache[prop];
		}

		return symbols;
	};
}

exports["default"] = Symbol;
module.exports = exports["default"];