How to pass session attribute to Websocket on creation?

I’m making a basic chat application with JSTL and Jakarta WebSockets but need to be able to pass a user’s group code to the websocket on open. I thought about adding the following meta tag to the HTML file

<meta name="group" content="${group}"/>

since “group” is stored as a session attribute. I then try to access this data in the following javascript file (where the websocket is created). Unfortunately I cannot do this since document doesn’t exist outside of functions. I added a comment to the line I am referring to.

var wsUrl;
if (window.location.protocol == 'http:') { wsUrl = 'ws://'; }
else { wsUrl = 'wss://'; }

var group = document.querySelector('meta[name=group]').content; //How can i access this info??
var socket = new WebSocket(wsUrl + window.location.host + "/ChoreSplitter/message?group=" + "123");
        
socket.onmessage = function(event) {
    var mySpan = document.getElementById("chat");
    mySpan.innerHTML += event.data;
};
     
socket.onerror = function(event) {
    console.log("Chat Error ", event)
} 

function sendMsg() {
    var msg = document.getElementById("msg").value;
    if (msg) {
        socket.send(msg);
    }
    document.getElementById("msg").value = "";
}

Anyone have suggestions for a better way to pass this session data on creation of my web socket? Could I potentially send this data from a servlet to the ServerEndpoint?