javascript - 如何检测从 Websocket 服务器发送的消息

Question

我有一个小型 Web 应用程序，用于监听来自 Websocket 服务器的传入消息。我像这样接收它们

const webSocket = new WebSocket("wss://echo.websocket.org");
webSocket.onopen = event => webSocket.send("test");
webSocket.onmessage = event => console.log(event.data);

但发送服务器更复杂。可能会出现多种类型的消息，例如“UserConnected”、“TaskDeleted”、“ChannelMoved”
如何检测发送的消息类型？现在我将代码修改为

const webSocket = new WebSocket("wss://echo.websocket.org");

webSocket.onopen = event => {
  const objectToSend = JSON.stringify({
    message: "test-message",
    data: "test"
  });

  webSocket.send(objectToSend);
};

webSocket.onmessage = event => {
  const objectToRead = JSON.parse(event.data);

  if (objectToRead.message === "test-message") {
    console.log(objectToRead.data);
  }
};

那么我是否必须从服务器发送一个包含“方法名称”/“消息类型”的对象，例如“TaskDeleted”确定在客户端执行的正确方法？那会导致一个很大的 switch case 语句，不是吗？
有没有更好的方法？

Answer 1

您可以通过直接映射方法来避免大的 switch-case 语句:

// List of white-listed methods to avoid any funny business
let allowedMethods = ["test", "taskDeleted"];

function methodHandlers(){
  this.test = function(data)
  {
     console.log('test was called', data);
  }

  this.taskDeleted = function(data)
  {
     console.log('taskDeleted was called', data);
  }
}


webSocket.onmessage = event => {
  const objectToRead = JSON.parse(event.data);
  let methodName = objectToRead.message;
  if (allowerMethods.indexOf(methodName)>=0)
  {
     let handler = new methodHandlers();
     handler[methodName](data);
  }
  else
  {
     console.error("Method not allowed: ", methodName)
  }
 };