js 判断设备及安卓设备判断不准确问题

<!-- web 获取 设备类型.注意: 一旦app端设置了userAgent 将会覆盖设置自带的ua -->
  <script>
    var agent = "";
    function isAndroid() {
      agent = navigator.userAgent.toLowerCase();
      let result = {
        device: function () {
          if (/windows/.test(agent)) {
            return 'windows pc';
          } else if (/iphone|ipod/.test(agent) && /mobile/.test(agent)) {
            return 'iphone';
          } else if (/ipad/.test(agent) && /mobile/.test(agent)) {
            return 'ipad';
          } else if (/android/.test(agent) && /mobile/.test(agent)) {
            return 'android';
          } else if (/linux/.test(agent)) {
            return 'linux pc';
          } else if (/mac/.test(agent)) {
            return 'mac';
          } else {
            return 'other';
          }
        }(),
      };
      document.getElementById("agent").innerText = agent;
      document.getElementById("showAndroid").innerText = result.device;
      return result.device;
    }
  </script>

不准确的问题原因