getParams(url = window.location.href) {
        const query = this.getQueryString(url);
        if (query === undefined) {
            return undefined;
        }
        const params = {};
        const hashes = query.split('&');
        for(let i = 0; i < hashes.length; i++) {
            let hash = hashes[i].split('=');
            if (hash[0].indexOf('[]') !== -1) {
                // is array
                if (params[hash[0]] === undefined) {
                    params[hash[0]] = [];
                }
                params[hash[0]].push(hash[1]);
            } else {
                params[hash[0]] = hash[1];
            }
        }
        return params;
    }
Get URL params as object (name => value) or undefined if there are no query string
@param {String?} url
@returns {Object|undefined}