javascript闭包怎么在WebSockets中应用

function createWebSocketHandler(ws, connectionId) {     let isActive = true; // 这个变量被闭包捕获     const connectionStartTime = Date.now(); // 同样被捕获      ws.onmessage = (event) => {         if (!isActive) {             console.log(`Connection ${connectionId} is inactive, ignoring message.`);             return;         }         console.log(`Message from ${connectionId}: ${event.data}`);         // 这里可以访问 connectionId 和 isActive         // 比如根据 connectionId 路由消息到特定用户     };      ws.onclose = () => {         isActive = false; // 更新状态，这个状态只对当前连接有效         const duration = Date.now() - connectionStartTime;         console.log(`Connection ${connectionId} closed after ${duration}ms.`);         // 清理与 connectionId 相关的资源     };      ws.onerror = (error) => {         console.error(`Error on connection ${connectionId}:`, error);         // 记录错误，并可能关闭连接     };      // 返回一些公共接口，如果需要的话     return {         getConnectionId: () => connectionId,         isConnectionActive: () => isActive     }; }  // 假设这是服务器端或客户端创建连接的逻辑 // const newWs = new WebSocket('ws://localhost:8080'); // createWebSocketHandler(newWs, 'user-123');

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// 假设这是在处理新的WebSocket连接时 wss.on('connection', function connection(ws, req) {     const userId = getUserIdFromRequest(req); // 从请求中解析用户ID，这可能是认证后的结果     const userSessionData = {         id: userId,         lastActive: Date.now(),         // ...其他用户相关数据     };      // 将 userSessionData 通过闭包“绑定”到 ws 的事件处理器上     ws.on('message', function incoming(message) {         // 在这里，我们可以直接访问到 userSessionData         console.log(`Received message from user ${userSessionData.id}: ${message}`);         // 根据 userSessionData.id 将消息广播到特定房间，或更新用户状态         userSessionData.lastActive = Date.now(); // 更新用户活跃时间         // ...     });      ws.on('close', function() {         console.log(`User ${userSessionData.id} disconnected.`);         // 清理与该用户相关的资源，比如从在线用户列表中移除     });      ws.on('error', function(error) {         console.error(`Error for user ${userSessionData.id}:`, error);     });      // 也可以将 ws 实例和 userSessionData 存储在一个全局映射中，方便通过 userId 查找 ws 实例     // activeConnections.set(userId, ws); });

function setupHeartbeat(ws, interval = 30000) {     let lastPongTime = Date.now();     let heartbeatIntervalId;      ws.onmessage = (event) => {         if (event.data === 'pong') {             lastPongTime = Date.now();             // console.log('Received pong, updating lastPongTime');         }         // ...处理其他消息     };      // 启动心跳     heartbeatIntervalId = setInterval(() => {         if (Date.now() - lastPongTime > interval * 2) { // 如果长时间没收到pong             console.warn('Heartbeat timeout, closing connection.');             ws.close();             clearInterval(heartbeatIntervalId);         } else {             ws.send('ping');         }     }, interval);      ws.onclose = () => {         clearInterval(heartbeatIntervalId); // 连接关闭时清除定时器         console.log('Heartbeat stopped for this connection.');     };      ws.onerror = () => {         clearInterval(heartbeatIntervalId);         console.error('Heartbeat stopped due to error.');     }; }  // const clientWs = new WebSocket('ws://localhost:8080'); // setupHeartbeat(clientWs);

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function createReconnectableWebSocket(url, options = {}) {     const { maxAttempts = 10, initialDelay = 1000 } = options;     let ws = null;     let reconnectAttempts = 0;     let reconnectTimeoutId = null;      const connect = () => {         ws = new WebSocket(url);          ws.onopen = () => {             console.log('WebSocket connected.');             reconnectAttempts = 0; // 成功连接后重置尝试次数             clearTimeout(reconnectTimeoutId); // 清除任何待执行的重连定时器             // 可以在这里触发一个 onConnect 回调             if (options.onConnect) options.onConnect(ws);         };          ws.onmessage = (event) => {             // console.log('Received message:', event.data);             if (options.onMessage) options.onMessage(event.data);         };          ws.onclose = (event) => {             console.log('WebSocket disconnected:', event.code, event.reason);             ws = null; // 清空旧的ws实例              if (reconnectAttempts < maxAttempts) {                 const delay = initialDelay * Math.pow(2, reconnectAttempts);                 reconnectAttempts++;                 console.log(`Attempting to reconnect in ${delay / 1000}s... (Attempt ${reconnectAttempts})`);                 reconnectTimeoutId = setTimeout(connect, delay); // 闭包捕获 connect 函数             } else {                 console.error('Max reconnect attempts reached. Giving up.');                 if (options.onMaxAttemptsReached) options.onMaxAttemptsReached();             }             if (options.onClose) options.onClose(event);         };          ws.onerror = (error) => {             console.error('WebSocket error:', error);             // 错误通常也会触发 onclose，所以这里不需要额外的重连逻辑             if (options.onError) options.onError(error);         };     };      connect(); // 首次连接      // 返回一个可以控制连接的对象，比如手动关闭     return {         send: (message) => {             if (ws && ws.readyState === WebSocket.OPEN) {                 ws.send(message);             } else {                 console.warn('WebSocket not open, message not sent.');             }         },         close: () => {             if (ws) {                 ws.close();                 clearTimeout(reconnectTimeoutId); // 手动关闭时也要清除重连定时器             }         }     }; }  // 使用示例： // const myWebSocket = createReconnectableWebSocket('ws://localhost:8080/chat', { //     onMessage: (data) => console.log('App received:', data), //     onConnect: (wsInstance) => console.log('App connected, ready to send!'), //     onMaxAttemptsReached: () => alert('无法连接到服务器，请检查网络！') // }); // myWebSocket.send('Hello server!');

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