获取浏览器摄像头，麦克风列表

 navigator.mediaDevices.enumerateDevices()
      .then(function(devices) {
        devices.forEach(function(device) {
          //audioinput   videoinput（视频）  audiooutput(音频)
           console.log('设备3:'+device.kind + ": " + device.label +
                   " id = " + device.deviceId);
        });

navigator.mediaDevices.getUserMedia({
            audio: {deviceId:deviceId},
            video: false,
          }).then(function (stream) {
            getAudioSuccess(stream);
          })["catch"](function (e) {
            getAudioFail(e);
          });