My code as below:

import { useEffect, useState } from "react";
import Meeting from "./util/Meeting";
export default function TestMeeting(){
    const [peerList, setPeerList] = useState();
    const [meeting, setMeeting] = useState();
    let peerName;
    let sUsrAg = navigator.userAgent;
    if (sUsrAg.indexOf("Edg") > -1) {
        peerName = "Edge";
    } else {
        if (sUsrAg.indexOf("Chrome") > -1) {
            peerName = "Chrome";
        } else {
            if (sUsrAg.indexOf("Firefox") > -1) {
                peerName = "Firefox";
            } else {
                if (sUsrAg.indexOf("Safari") > -1) {
                    peerName = "Safari";
                }
            }
        }
    }
    useEffect(() => {
        let temp = new Meeting();
        temp.setDebug(true);
        temp.on("data", param => {
            console.log("Data Event Recevied:" + JSON.stringify(param));
        })
        temp.on("initialPeerList", (newPeerList) => {
            console.log("initialPeerList event recevied");
            console.log(newPeerList);
            setPeerList(newPeerList);
        });
        temp.on("newPeer", (newPeer) => {
            console.log("newPeer event recevied");
            console.log(peerList);
        });
        temp.on("removePeer", socketId => {
            console.log("removePeer event recevied");
            
        });
        temp.on("stream", param => {
            console.log("A stream event received:" + JSON.stringify(param));
            
        })
        temp.join(peerName);
        setMeeting(temp);
    }, [peerName]);   
    return (
        <>
        </>
    )
}

The "initialPeerList" event is received first and the peerList state variable should be updated. After that, when the "newPeer"event is received, suppose the content of peerList state variable should not undefined, however, it does.

I have followed the page: useState set method not reflecting change immediately

However, it does not solve the problem.

Why is this like that and how would I be able to fix it?