NextJS, Socket.io: in the server-side, my third parameter which is a acknowledgement's callback returns to me: callback is not a function

Question

I'm using NextJS with Socket.IO. All the basics works good, now, I'm trying to make acknowledgement callback with an emit's function. I have follow it seems to me all the rules, but it doesn't work. I can't figure why.

Here my server.js snippet:

// listen for socket's connection
io.sockets.on("connection", (socket)=>{ 
  // socket.join('some room');

  // on connection, listen any event on join's channel 
  socket.on('join',(param, callback) => {
    console.log("callback: ", callback) 

    // some logs to appreciate if my URL's params follow the rules 
    console.log("!isRealString(param.name): ", !isRealString(param.name) )
    console.log(" !isRealString(param.room): ",  !isRealString(param.room))

    // if they fails to follow the rules, return an error 
    if(!isRealString(param.name) || !isRealString(param.room)){ 
      callback("Name and room are required") // not a function
    } 

      // if no error, returns a succeed's log -set in client side- 
    callback()      

});

my client's side snippet:

// set socket.io variable 
this.socket=io(); 

   // on connect, trigger a function
   this.socket.on("connect", () => {

      // get the window's URL  
      // and pass an helper which translate URL's queries in javascript's object
      var param =deparam(window.location.search);

      // then emit an event on joint channel
      // three parameters: channel, param, acknowledgement callback
      this.socket.emit("join", param, function(err){ 

      // if there is an error, alert the user then redirect
      if(err){ 
         alert(err);
         Router.replace("/");
      } 
      // errorFree? display a succeed's message
      else{ 
         console.log("No error");
      }
   });
});

It seems to me all is good if I believe the googling I have done. Maybe is NextJS who have some quirk behaviors, Any hint would be great, thanks

Answer 1

window object would not always be defined in next js, but you can check if its SSR by using

  process.browser

before calling window.location to avoid error