Rocket.Chat/app/ui-utils/client/config.js

import { Meteor } from 'meteor/meteor';

const url = new URL(window.location);
const keys = new Set();
export const getConfig = (key) => {
	keys.add(key);
	return url.searchParams.get(key) || Meteor._localStorage.getItem(`rc-config-${ key }`);
};