得到一个类型错误说我的websocket变量是未定义的

Question

我的页面正在播放视频，我正在尝试捕获帧并通过websocket将它们发送到服务器。

我已经成功地建立了与服务器的连接，并完成了websocket握手。

然而，我得到以下错误在我的postVideoToServer()函数:

"TypeError: clientSocket is undefined" index.html:60:5

clientsocket实际上是客户端用来与服务器通信的套接字。我已经在clientSocket.onopen中使用这个变量成功地将数据发送到服务器。

我做了一些研究，发现这意味着一个值不是预期的类型。我还是不明白。如有任何解释，将不胜感激。

这是我的js代码的一部分。如果需要更多，请告诉我。

  var bStop = true;
  var bOldBrowser = false;
  var video;
  var streamRecorder;
  var webcamstream;
  var clientSocket;
 function postVideoToServer(clientSocket,frame) 
 { 
      clientSocket.send(frame);
 }
 function draw(v, cc, w, h, c, clientSocket) 
 {
       cc.drawImage(v, 0, 0, w, h);  //draw video frame on canvas
       var frameData =c.toDataURL(); //turn canvas to raw png format
       postVideoToServer(clientSocket,frameData);
       if(!bStop) 
           setTimeout( function() { draw(v, cc, w, h, c, clientSocket) }, 40);   //40 * 25 = 1000 ==> draw canvas every 40 ms to have 25FPS
  }
  function startRecording(video, clientSocket)
  {       
       video = document.querySelector('video');
       var canvas = document.getElementById('canvas');
       var canvasContext = canvas.getContext('2d');
       var width = video.videoWidth;
       var height = video.videoHeight;
       canvas.width = width;
       canvas.height = height; 
       bStop = false;
      //establish connection with server
      establishSocketConnection(clientSocket,"ws://localhost:3000/web/project/Server.php");
      draw(video, canvasContext, width, height, canvas, clientSocket)            
   }

    function establishSocketConnection(clientSocket,URL)
    {
        clientSocket = new WebSocket(URL); //create socket to server
        clientSocket.onopen = function (e) 
        {
            console.log("socket open");
        }
        clientSocket.onclose = function (e) 
        {
            console.log("Socket connection closed : "+e);
        }
        clientSocket.onerror = function(error) 
        {
            alert("Failed to connect to server...Please try again later.");
        };               
   }    

当我点击

下面的按钮时，开始录制功能被触发

<button onclick="startRecording(video)" class="recordbutton">Turn camera on</button>

Answer 1

您需要从所有函数中删除clientSocket参数，只使用全局变量。因为即使你调用:

 onclick="startRecording(video, clientSocket)"

clientSocket将是未定义的(你没有传递任何值)，你不能从函数内部改变它。