SyntaxError：意外的标记，预期的“，”

Question

我是 ReactJS 的新手。 这是我的第一个 React 程序。 这是一个动态页面。 我正在使用 firebase db。

     import React, {useEffect,useState} from 'react';
        import './Sidebar.css';
        import {Avatar,IconButton} from '@material-ui/core';
        import DonutLargeIcon from '@material-ui/icons/DonutLarge';
        import ChatIcon from '@material-ui/icons/Chat';
        import MoreVerIcon from '@material-ui/icons/MoreVert';
        import SearchOutline from '@material-ui/icons/SearchOutlined'
        import SidebarChat from './SidebarChat';
        import db from './firebase';
        
        function Sidebar() {
          const [rooms, setRooms] = useState([])
        
          useEffect(() => {
           db.collection('rooms').onSnapshot((snapshot)
            =>
            setRooms(
                    snapshot.docs.map((doc) => ({
                    id: doc.id,
                    data: doc.data(),
            }))
            )
          );
               
          }, []);
        
            return (
              <div className="sidebar">
                <div className="sidebar_header">
                  <Avatar />
                  <div className="sidebar_headerRight">
                    <IconButton>
                      <DonutLargeIcon />
                    </IconButton>
                    <IconButton>
                      <ChatIcon />
                    </IconButton>
                    <IconButton>
                      <MoreVerIcon />
                    </IconButton>
                  </div>
                </div>
        
                <div className="sidebar_search">
                  <div className="sidebar_searchContainer">
                  <SearchOutline />
                  <input placeholder="Search or start new chat" type="text" />
                  </div>
                </div>
                <div className="sidebar_chats">
                  <SidebarChat addNewChat/>
                  {rooms.map(room => (<SidebarChat key ={room.id} id={room.id}
                  name={room.data.name}/>
                  ))}
                </div>
              </div>
            );
        }
        
        export default Sidebar

错误是：

 Unexpected token, expected "," (16:4)
  14 |   useEffect(() => {
  15 |    db.collection('rooms').onSnapshot((snapshot)
> 16 |     =>
     |     ^
  17 |     setRooms(
  18 |             snapshot.docs.map((doc) => ({
  19 |             id: doc.id,

Answer 1

将=>与参数列表放在同一行。

  const funcWithNoError = () => {
  }

  const funcWithError = ()
  =>
  {
  }

在你的情况下：

  useEffect(() => {
   db.collection('rooms').onSnapshot((snapshot) =>
    setRooms(
            snapshot.docs.map((doc) => ({
            id: doc.id,
            data: doc.data(),
    }))
    )
  );
       
  }, []);