react中使用 websocket，使用socket.io库
参考官网地址： https://socket.io/zh-CN/docs/v4/client-installation/#from-npm

1.安装

npm install socket.io-client

2.示例代码

import React, { useEffect, useRef, useState } from "react";
import classNames from "classnames";
import { formatDate } from "../../utils/format";
import "./index.css";

// https://socket.io/zh-CN/docs/v4/client-installation/#from-npm
import { io } from "socket.io-client";
const socket = io("ws://localhost:8888"); // 连接，握手

function Chat() {
  // 用户列表
  const [usersList, setUsersList] = useState([]);
  // 历史记录
  const [historyData, setHistoryData] = useState([]);
  // 当前用户是否是自己
  const [mine, setMine] = useState("");
  // 要发送的消息
  const [message, setMessage] = useState("");

  useEffect(() => {
    // 当前聊天室的用户数组 -- 有新用户进入/老用户退出/自己进入
    socket.on("$updateUser", (users) => {
      console.log(users, "users");
      setUsersList(users);
    });
    // 分配的用户名称 -- 自己进入
    socket.on("$name", (name) => {
      console.log(name, "name");
      setMine(name);
    });
    // 历史聊天记录  -- 自己进入
    socket.on("$history", (history) => {
      console.log(history, "history");
      setHistoryData(history);
    });
    // 其他人发送消息
    socket.on("$message", (message) => {
      console.log(message, 123);
      setHistoryData([...historyData, message]);
    });
    return () => {
      socket.off("$updateUser");
      socket.off("$name");
      socket.off("$history");
      socket.off("$message");
    };
  }, [historyData]);

  const chatAreaRef = useRef();
  //  当聊天区高度超出后，设置滚动条在最下面
  useEffect(() => {
    chatAreaRef.current.scrollTop = chatAreaRef.current.scrollHeight;
  }, [historyData]);

  //   发送消息
  const handleKeyDown = (e) => {
    if (e.key === "Enter") {
      e.preventDefault(); // 阻止默认的换行行为
      const content = message.trim();
      if (!content) return;
      const messageInfo = {
        name: mine,
        content: content,
        data: Date.now(),
      };
      setHistoryData([...historyData, messageInfo]); // 将消息添加到历史记录里面
      socket.emit("$message", message); // 将消息发送到服务器
      setMessage(""); // 清空textarea
    }
  };

  return (
    <section className="chat-container">
      <aside className="chat-users">
        <div className="title">聊天室成员</div>
        {usersList.length > 0 &&
          usersList.map((item, index) => (
            <div key={index} className="per-user">
              {item}
            </div>
          ))}
      </aside>
      <section className="chat-main">
        <div className="chat-user">{mine}</div>
        <div className="chat-area" ref={chatAreaRef}>
          {historyData.length > 0 &&
            historyData.map((item, index) => (
              <div
                key={index}
                className={classNames("chat-item", {
                  mine: mine === item.name,
                })}
              >
                <div className="name">{item.name}</div>
                <div className="content">{item.content}</div>
                <div className="date">{formatDate(item.date)}</div>
              </div>
            ))}
        </div>
        <div className="chat-message">
          <textarea
            name="message"
            value={message}
            onChange={(e) => {
              setMessage(e.target.value);
            }}
            onKeyDown={handleKeyDown}
          ></textarea>
        </div>
      </section>
    </section>
  );
}

export default Chat;

3.效果：