I am making a real time multiplayer game with socket.io and node.js, I have a html file that runs a public script to connect to the server and run commands, as well as defining the library I need with

<script src="https://code.jquery.com/jquery-2.2.2.min.js"></script>

I have a connect and disconnect function in thew public js file that has these functions:

// send join request
function joinlobby(room) {
  socket.emit("userJoined", room);
}

// emit when a player leaves
function leavelobby(room) {
  socket.emit("userLeft", room);
}

and whenever I create a new socket within the function with something like

// emit when a player leaves
function leavelobby(room) {
  let socket = io();
  socket.emit("userLeft", room);
}

it will run correctly, however with both having a separate connection it causes issues. I was trying to have them use the same connection by having let socket = io(); placed above the functions to use the same socket, however when the program hits that line it stops running the file without throwing an error

How could I use a single connection to the server, and/or why is the program disconnecting when I define the socket outside a function?

Edit for clarity: The issue isn't wanting a single connection for every client, but rather each client has multiple connections whenever I define the socket in each respective function. I am aiming at only having 1 connection for each client but the line throws an error

I'm sorry for the ambiguity, I'm new to asking questions on here