使用WebRTC调用addTrack方法时报错

Question

navigator.mediaDevices.getUserMedia({ video: true, audio: true }).then(stream => {
                  this.localVideo.srcObject = stream;
                  stream.getTracks().forEach(track => {
                    console.log(this.peer)
                    this.peer.addTrack(track, stream);
                  });
                });

错误提示：TypeError: _this3.peer.addTrack is not a function
求指教！