The Tor Browser / file revision

 /* This Source Code Form is subject to the terms of the Mozilla Public

  * License, v. 2.0. If a copy of the MPL was not distributed with this

  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

 "use strict";

 module.metadata = {

   "stability": "unstable"

 };

 const create = Object.create;

 const prototypeOf = Object.getPrototypeOf;

 /**

  * Returns a new namespace, function that may can be used to access an

  * namespaced object of the argument argument. Namespaced object are associated

  * with owner objects via weak references. Namespaced objects inherit from the

  * owners ancestor namespaced object. If owner's ancestor is `null` then

  * namespaced object inherits from given `prototype`. Namespaces can be used

  * to define internal APIs that can be shared via enclosing `namespace`

  * function.

  * @examples

  *    const internals = ns();

  *    internals(object).secret = secret;

  */

 function ns() {

   const map = new WeakMap();

   return function namespace(target) {

     if (!target)        // If `target` is not an object return `target` itself.

       return target;

     // If target has no namespaced object yet, create one that inherits from

     // the target prototype's namespaced object.

     if (!map.has(target))

       map.set(target, create(namespace(prototypeOf(target) || null)));

     return map.get(target);

   };

 };

 // `Namespace` is a e4x function in the scope, so we export the function also as

 // `ns` as alias to avoid clashing.

 exports.ns = ns;

 exports.Namespace = ns;