polyfill-service/polyfills/WeakMap/polyfill.js

A polyfill combinator

/**
 * @license
 *
 * Portions of this polyfill are a derivative work of the Polymer project, which requires the following licence notice:
 *
 * Copyright (c) 2014 The Polymer Project Authors. All rights reserved.
 * This code may only be used under the BSD style license found at http://polymer.github.io/LICENSE.txt
 * The complete set of authors may be found at http://polymer.github.io/AUTHORS.txt
 * The complete set of contributors may be found at http://polymer.github.io/CONTRIBUTORS.txt
 * Code distributed by Google as part of the polymer project is also
 * subject to an additional IP rights grant found at http://polymer.github.io/PATENTS.txt
 */

 (function() {
	var defineProperty = Object.defineProperty;
	var counter = Date.now() % 1e9;

	var WeakMap = function WeakMap (data) {
		this.name = '__st' + (Math.random() * 1e9 >>> 0) + (counter++ + '__');

		// If data is iterable (indicated by presence of a forEach method), pre-populate the map
		data && data.forEach && data.forEach(function (item) {
			this.set.apply(this, item);
		}, this);
	};

	WeakMap.prototype["set"] = function(key, value) {
		if (typeof key !== 'object' && typeof key !== 'function')
			throw new TypeError('Invalid value used as weak map key');

		var entry = key[this.name];
		if (entry && entry[0] === key)
			entry[1] = value;
		else
			defineProperty(key, this.name, {value: [key, value], writable: true});
		return this;
	};
	WeakMap.prototype["get"] = function(key) {
		var entry;
		return (entry = key[this.name]) && entry[0] === key ?
				entry[1] : undefined;
	};
	WeakMap.prototype["delete"] = function(key) {
		var entry = key[this.name];
		if (!entry || entry[0] !== key) return false;
		entry[0] = entry[1] = undefined;
		return true;
	};
	WeakMap.prototype["has"] = function(key) {
		var entry = key[this.name];
		if (!entry) return false;
		return entry[0] === key;
	};

	WeakMap.prototype.constructor = WeakMap;
	WeakMap.name = "WeakMap";


	this.WeakMap = WeakMap;
}());