If object does not have key, add it.
此脚本不应直接安装，它是一个供其他脚本使用的外部库。如果您需要使用该库，请在脚本元属性加入：// @require https://update.greasyfork.org/scripts/427473/937466/object_setDefault.js
// ==UserScript==
// @name object_setDefault
// @namespace bo.gd.an[at]rambler.ru
// @version 0.5
// @description If object does not have key, add it.
// @author Bogudan
// @license LGPLv3
// ==/UserScript==
(function () {
function setDefault (key, value) {
if (!(key in this))
this [key] = value;
}
Object.defineProperty (Object.prototype, 'setDefault', {
get : () => setDefault,
set : () => {},
});
}) ();