Data received from socket.io is not immediately reflected in the status
P粉043566314
P粉043566314 2023-09-17 15:04:28
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When app.js receives data sent from the server (displayed in the console), setState does not refresh the web page with the new data. In the line console.log("Received data queue:", data.queue), it also returns undefined. I expected it to be a specific value because in the line console.log(data) it has the value stored under the "queue" key.

This is my code:

import React, { Component } from "react";
import { TransitionGroup, CSSTransition } from "react-transition-group";
import "./chat.css";
import "./styles.css";
import "./queue.css";
import Chat from "./chat";
import io from "socket.io-client";

class App extends Component {
  constructor(props) {
    super(props);
    this.state = {
      queue: [],
      instruction: "",
      user: "",
      hal: "",
      status: "waiting"
    };
  }
  componentDidMount() {
    const socket = io("http://localhost:5000");
    socket.on("connect", () => {
      console.log("Connected to the socket server");
    });

    socket.on("queueData", (data) => {
      console.log("Received data:", data);
      console.log("Received data queue:", data.queue);
      this.setState({ queue: data.queue }, () => {
        console.log(this.state.queue);
      });
      this.setState({ instruction: data.instruction }, () => {
        console.log(this.state.instruction);
      });
      // other attributes, user, hal, status ignored here for simplicity
    });

    this.socket = socket;
  }

  componentWillUnmount() {
    this.socket.disconnect();
  }


  renderData = () => {
    console.log("rendered queue", this.state.queue);
    if (this.state.queue === undefined) {
      return null;
    }
    return this.state.queue.map((task, index) => (
      
        
{task} {index === 0 && this.state.status === "working" && (
)}
)); }; render() { return (
{this.renderData()}
Instruction: {this.state.instruction}
); } } export default App;

I want the webpage to refresh immediately when new data is received. I've added a callback function to setState, but it still doesn't work.

P粉043566314
P粉043566314

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P粉617597173

When using socket.io in your application, you may experience delays in updating status after receiving data due to a number of factors. For example, the asynchronous nature of socket.io, state management issues, event handling, React component life cycle, etc.

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