getQueryString(url = window.location.href) {
        const pos = url.indexOf('?');
        let hashPos = url.indexOf('#');
        if (hashPos > -1) {
            return pos > -1 ? decodeURI(url.slice(pos + 1, hashPos)) : undefined;
        }
        return pos > -1 ? decodeURI(url.slice(pos + 1)) : undefined;
    }
Get URL query string (after ?) or false if there are no query string
@param {String?} url
@returns {String|undefined}