How to send a WebSocket message conditionally?

Question

I'm using javascript and the ws package from expressjs to set up my server. I'm building a chat app for my portfolio and initially my idea was to have the client tell the server which chats the user is in (subscriptions) and store them in a subscriptions array. for(leti=0;i<subscriptions.length;i++){wss.clients.forEach((client)=>{if(json.bod

P粉198749929 · Answer

First, you need to maintain a method that maps each client to the chat ID to which it is subscribed. You can do this using JavaScript's Map, where the keys are client objects and the values are an array of chat IDs they are subscribed to:

const subscriptionsMap = new Map();

When a client connects to WebSocket, store its subscription information in subscriptionsMap. When clients disconnect, make sure to remove their subscriptions from the map:

wss.on('connection', (client) => {
  // 处理客户端连接

  // 假设`json.body.subscriptions`包含客户端订阅的聊天ID数组
  subscriptionsMap.set(client, json.body.subscriptions);

  // 处理客户端断开连接
  client.on('close', () => {
    subscriptionsMap.delete(client);
    // 执行任何必要的清理操作
  });
});

Now when you receive a message that needs to be sent to a client in a specific chat, iterate through the connected clients and only send the message to those clients subscribed to the relevant chat ID:

// 假设`json.body.chatId`包含消息的聊天ID
const chatId = json.body.chatId;

wss.clients.forEach((client) => {
  if (subscriptionsMap.has(client) && subscriptionsMap.get(client).includes(chatId)) {
    client.send(message);
  }
});