function isUrl(string) {
        var urlRegexp = /^(https?:\/\/|ftps?:\/\/)?([a-z0-9%-]+\.){1,}([a-z0-9-]+)?(:(\d{1,5}))?(\/([a-z0-9\-._~:/?#[\]@!$&'()*+,;=%]+)?)?$/i;
        return urlRegexp.test(string);
    }
Check if a string represents a valid url
@return boolean