使用WebRTC如何选择麦克风和摄像头？

// 获取设备列表
navigator.mediaDevices.enumerateDevices()
  .then(function(devices) {
    let audioDevices = [];
    let videoDevices = [];

    // 筛选麦克风和摄像头设备
    devices.forEach(function(device) {
      if (device.kind === 'audioinput') {
        audioDevices.push(device);
      } else if (device.kind === 'videoinput') {
        videoDevices.push(device);
      }
    });

    // 显示设备选项
    let audioSelect = document.getElementById('audio-select');
    let videoSelect = document.getElementById('video-select');

    audioDevices.forEach(function(device) {
      let option = document.createElement('option');
      option.value = device.deviceId;
      option.text = device.label;
      audioSelect.appendChild(option);
    });

    videoDevices.forEach(function(device) {
      let option = document.createElement('option');
      option.value = device.deviceId;
      option.text = device.label;
      videoSelect.appendChild(option);
    });
  })
  .catch(function(err) {
    console.error('获取设备列表失败：', err);
  });

// 用户选择设备
let audioSelect = document.getElementById('audio-select');
let videoSelect = document.getElementById('video-select');

audioSelect.addEventListener('change', function() {
  let selectedAudioDeviceId = audioSelect.value;
  // 应用选择的麦克风设备
  applySelectedDevice(selectedAudioDeviceId, 'audio');
});

videoSelect.addEventListener('change', function() {
  let selectedVideoDeviceId = videoSelect.value;
  // 应用选择的摄像头设备
  applySelectedDevice(selectedVideoDeviceId, 'video');
});

// 应用选择的设备
function applySelectedDevice(deviceId, deviceType) {
  let constraints = {};
  constraints[deviceType] = { deviceId: deviceId };

  navigator.mediaDevices.getUserMedia(constraints)
    .then(function(stream) {
      // 在页面上显示媒体流
      let videoElement = document.getElementById('video-element');
      videoElement.srcObject = stream;
    })
    .catch(function(err) {
      console.error('获取媒体流失败：', err);
    });
}