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;

      }