How to send additional data on socket connection with JavaScript socket.io?

To send additional data on socket connection with JavaScript socket.io, we call the emit function with the data.

For instance, we write

socket.on("connect", () => {
  socket.emit("hello", data);
});

io.on("connection", (client) => {
  client.on("hello", (data) => {});
});

to call emit to emit the 'hello' event with the data we want to send to the client.