套接字io延迟一个事件

Question

I have connected socket io to Webhook and it succeeds. It can get information and can express But I'm stuck with one problem. When the desired value is displayed on the client-side, the response is delayed. For example, when the server-side detects an event will show on console.log(); But it won't show on the client-side. But when the server-side detects the event again (second time) The value saved the first time is sent to the client-side, and if the server detects the event again (third time) The second event value is sent to the client-side, which means it will delay the event one time. How can I fix this incident?

 // Server const app = require('express')(); const http = require('http').createServer(app); const io = require('socket.io', { transports: ['websocket', 'polling'] })(http, { cors: { origin:'*' } }); const bodyParser = require("body-parser"); PORT = 8080; io.on('connection', socket => { app.use(bodyParser.json()); app.post('/api', (req, res) => { let x = req.body[0]; let dates = x.created_date; let name = x.name; let watchlist = x.watchlist[Object]; if (watchlist == "Matched"){ console.log("Date :", dates) console.log("Name :", name) io.emit('FromAPI', dates, name); } else { console.log("Unmatch") } res.status(200).end("Successfully"); }); console.log('Socket connected'); socket.on('disconnect', () => { console.log('Socket disconnected')}); }); http.listen(PORT, () => { console.log(`Server : http://localhost: ${PORT}`); });

 // Client import { useEffect, useState } from 'react'; import io from 'socket.io-client'; const socket = io("http://localhost:8080", { transports: ['websocket', 'polling'] }); export default function App() { const [date, setDate] = useState(''); const [name, setName] = useState(''); const [hook_event, setHook_event] = useState([ { "date": date, "name": name}, { "date": date, "name": name} ]); useEffect(() => { socket.on('FromAPI', (date, name) => { setDate(date); setName(name); hook_event.unshift({"date": date, "name": name}); hook_event.pop(); }) }, []; return ( <> <p>Date : {hook_event[0].date} and {hook_event[0].name}</p> <p>Date : {hook_event[1].date} and {hook_event[1].name}</p> </> ); };

Answer 1

I think I found the problem.

    const [countState, setCountState] = useState() 

    useEffect(() => {
    socket.on('FromAPI', (date, name) => {
      setDate(date);
      setName(name);

      hook_event.unshift({"date": date, "name": name});
      hook_event.pop();
      setCountState(hook_event[0])
    })
    }, [setCountState]; // update setCountState