Socket online status frontend

backend/socket/socket.js

@@ -11,12 +11,23 @@ const io = new Server(server, {
     }
 })
 
+const userSocketMap = {}; // {userId: socketId}
+
 io.on('connection', (socket) => {
     console.log("user has connected", socket.id);
 
-    //socket.on is a listener for the events; can be used on both client and server side
+    //add user to socketmap when connecting
+    const userId = socket.handshake.query.userId;
+    if (userId != "undefined") userSocketMap[userId] = socket.id;
+
+    // io.emit() is an emitter for the connected clients; sends events to all connected clients
+    io.emit("getOnlineUsers", Object.keys(userSocketMap))
+    // socket.on is a listener for the events; can be used on both client and server side
     socket.on('disconnect', () => {
-        console.log('user disconnected', socket.id)
+        console.log('user disconnected', socket.id);
+        //delete user from socketmap and update online users when disconnecting
+        delete userSocketMap[userId];
+        io.emit('getOnlineUsers', Object.keys(userSocketMap));
     })
 })
 export {app, io, server}