is_weixn() {
        let ua = navigator.userAgent.toLowerCase();
        if (ua.match(/MicroMessenger/i) == "micromessenger" || ua.match(/WeiBo/i) == "weibo") {
          return true;
        } else if (ua.indexOf('mobile mqqbrowser') > -1 || ua.indexOf('webp') > -1) {
          return true;
        } else if (ua.indexOf('iphone') > -1 || ua.indexOf('mac') > -1) {
          if (ua.indexOf('qq') > -1) {
            return true;
          }
        }
        return false;
      }