无法显示参与者视频

Question

我无法显示远程参与者视频。 我收到无法读取未定义的属性“值” 因为没有参与者，所以请提出建议。

function roomJoined(room) {
console.log(room);
window.room = activeRoom = room;

var previewContainer = angular.element('#local-media');

  attachParticipantTracks(room.localParticipant, previewContainer[0]);

room.on('participantConnected', function(participant) {

participant.tracks.forEach(function(participant) {
    //log("Already in Room: '" + participant.identity + "'");
    var previewContainerPat = angular.element('#remote-media');
    console.log(previewContainerPat);
    attachParticipantTracks(participant, previewContainerPat[0]);
  });

  room.on('trackAdded', function(track, participant) {
    //log(participant.identity + " added track: " + track.kind);
    var previewContainer = angular.element('#remote-media');
    attachTracks([track], previewContainer[0]);
  });
});




room.on('trackRemoved', function(track, participant) {
  //log(participant.identity + " removed track: " + track.kind);
  detachTracks([track]);
});


room.on('participantDisconnected', function(participant) {
  //log("Participant '" + participant.identity + "' left the room");
 // detachParticipantTracks(participant);
});


room.on('disconnected', function() {

  if (previewTracks) {
    previewTracks.forEach(function(track) {
      track.stop();
    });
    previewTracks = null;
  }

  room.participants.forEach(detachParticipantTracks);
  activeRoom = null;

});
}

function attachTracks(tracks, container) {
tracks.forEach(function(track) {
container.appendChild(track.attach());
});
}

function attachParticipantTracks(participant, container, isLocal) {
var tracks = getTracks(participant);
attachTracks(tracks, container, isLocal);
}

function getTracks(participant) {
return Array.from(participant.tracks.values()).filter(function (publication) {
return publication.track;
}).map(function (publication) {
return publication.track;
});
}`

预期结果：应该为远程参与者显示视频

实际结果：抛出错误：-无法读取未定义的属性“值” 因为没有参与者。曲目