michael@0: /* This Source Code Form is subject to the terms of the Mozilla Public
michael@0:  * License, v. 2.0. If a copy of the MPL was not distributed with this
michael@0:  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
michael@0: 
michael@0: "use strict";
michael@0: 
michael@0: module.metadata = {
michael@0:   "stability": "unstable"
michael@0: };
michael@0: 
michael@0: const create = Object.create;
michael@0: const prototypeOf = Object.getPrototypeOf;
michael@0: 
michael@0: /**
michael@0:  * Returns a new namespace, function that may can be used to access an
michael@0:  * namespaced object of the argument argument. Namespaced object are associated
michael@0:  * with owner objects via weak references. Namespaced objects inherit from the
michael@0:  * owners ancestor namespaced object. If owner's ancestor is `null` then
michael@0:  * namespaced object inherits from given `prototype`. Namespaces can be used
michael@0:  * to define internal APIs that can be shared via enclosing `namespace`
michael@0:  * function.
michael@0:  * @examples
michael@0:  *    const internals = ns();
michael@0:  *    internals(object).secret = secret;
michael@0:  */
michael@0: function ns() {
michael@0:   const map = new WeakMap();
michael@0:   return function namespace(target) {
michael@0:     if (!target)        // If `target` is not an object return `target` itself.
michael@0:       return target;
michael@0:     // If target has no namespaced object yet, create one that inherits from
michael@0:     // the target prototype's namespaced object.
michael@0:     if (!map.has(target))
michael@0:       map.set(target, create(namespace(prototypeOf(target) || null)));
michael@0: 
michael@0:     return map.get(target);
michael@0:   };
michael@0: };
michael@0: 
michael@0: // `Namespace` is a e4x function in the scope, so we export the function also as
michael@0: // `ns` as alias to avoid clashing.
michael@0: exports.ns = ns;
michael@0: exports.Namespace = ns;