无法通过WebRTC应用程序接口在Mozilla浏览器中检查输出设备，如扬声器

navigator.mediaDevices.enumerateDevices()
  .then(function(devices) {
    devices.forEach(function(device) {
      console.log(device.kind + ": " + device.label +
                  " id = " + device.deviceId);
    });
  })
  .catch(function(err) {
    console.log(err.name + ": " + err.message);
  });

navigator.mediaDevices.enumerateDevices()
  .then(function(devices) {
    var outputDevices = devices.filter(function(device) {
      return device.kind === 'audiooutput';
    });
    outputDevices.forEach(function(device) {
      console.log(device.label + " id = " + device.deviceId);
    });
  })
  .catch(function(err) {
    console.log(err.name + ": " + err.message);
  });

var audioContext = new AudioContext();
var audioElement = document.createElement('audio');
audioElement.src = 'audio.mp3';

navigator.mediaDevices.getUserMedia({ audio: true })
  .then(function(stream) {
    var source = audioContext.createMediaStreamSource(stream);
    var destination = audioContext.destination;
    source.connect(destination);
  })
  .catch(function(err) {
    console.log(err.name + ": " + err.message);
  });