단순한 구현을 위해 DB 대신 userTable.txt 파일을 생성하여 사용하였습니다

talkUserCheckServer.js

var express = require('express'),
    app = express(),
    http = require('http').Server(app),
    // [email protected]
    io = require('socket.io')(http),
    fs = require('fs'),
    cors = require('cors'),
    path = require('path'),
    userTablePath = `${path.join(__dirname, './userTable')}`;
    
    http.listen(3003);
    // app.listen(3000);

    app.use(cors());

    app.get('/', (req,res) => res.json(123));
    app.get('/login', async (req,res) => {
        var id = req.query.id;
        if(id == null) return res.json(false);
        var userFile = await fs.readFileSync(userTablePath);
        var userTable = JSON.parse(userFile);
        var loginCheck = userTable.map((ele, index, arr) => {
            if(ele.id === id){
                return true;
            }
            return null;
        }).filter((ele, index, arr) => {if(ele !==null) return ele});;
        if(!loginCheck[0]) return res.json(false);
        var updateUserTable = userTable.map((ele, index, arr) => {
            if(ele.id === id){
                ele.on = true;
            }
            return ele;
        });
        try {
            await fs.writeFileSync(userTablePath, JSON.stringify(updateUserTable));
            return res.json(true);   
        } catch (error) {
            return res.json(false);
        }
    });
    app.get('/logout', async (req,res) => {
        var id = req.query.id;
        if(id == null) return res.json(false);
        var userFile = await fs.readFileSync(userTablePath);
        var userTable = JSON.parse(userFile);
        var updateUserTable = userTable.map((ele, index, arr) => {
            if(ele.id === id){
                ele.on = false;
            }
            return ele;
        });
        try {
            await fs.writeFileSync(userTablePath, JSON.stringify(updateUserTable));    
            return res.json(true);
        } catch (error) {
            return res.json(false);
        }
    });
    app.get('/fds', async (req,res) => {
        var id = req.query.id;
        if(id == null) return res.json(false);
        var userFile = await fs.readFileSync(userTablePath);
        var userTable = JSON.parse(userFile);
        var userFds = userTable.map((ele, index, arr) => {
            if(ele.id === id){
                return ele.fds
            }
            return null;
        }).filter((ele, index, arr) => {if(ele !==null) return ele});
        var result = userFds[0].map((ele, index, arr) => {
            return userTable.map((ele2, index2, arr2) => {
                if(ele.name === ele2.id){
                    return {name: ele.name, on: ele2.on};
                }
                return null;
            }).filter((ele, index, arr) => {if(ele !==null) return ele})[0];
        }).filter((ele, index, arr) => {if(ele !==null) return ele});
        res.json(result);
    });

    io.on('connection', socket => {
        io.emit('userEvent', true);
        socket.on('userLogout', (data) => {
            io.emit('userEvent', true);
        });
    });