Core.Singleton = class extends _core {
    /**
     * Get singleton reference to object.
     * @param {string|jQuery} id
     * @param {object} parameters
     * @param {object} parameters.instance Modal/Page object reference
     */
    static get(id, parameters) {
        if (!parameters) {
            parameters = {};
        }

        if (
            parameters.prototype instanceof _core
            || parameters.prototype instanceof _page
            || parameters.prototype instanceof _modal
            || parameters instanceof _page
            || parameters instanceof _modal
        ) {
            parameters = {
                instance: parameters
            };
        }
        if (id instanceof jQuery) {
            if (!parameters.$container) {
                parameters.$container = id;
            }
            if (!id.attr('singleton-id')) {
                id.attr('singleton-id', 'singleton-' + uniqId());
            }
            id = id.attr('singleton-id');
        }
        let key = this.getClassName() + ':' + id;
        if (Core.Singleton.references[key]) {
            if (Core.Singleton.references[key].reinit(id, parameters) === false) {
                Core.Singleton.references[key] = null;
                return null;
            }
            return Core.Singleton.references[key];
        }
        let object = eval('new ' + this.getClassName());
        if (object.init(id, parameters) === false) {
            return null;
        }
        object._singletonId = key;
        Core.Singleton.references[key] = object;

        return object;
    }
};
Core.Singleton.references = {};