使用reactjs钩子时,为什么会出现“ TypeError:react__WEBPACK_IMPORTED_MODULE_1 ___ default.a.useState不是函数”错误?

时间:2019-01-17 16:00:22

标签: javascript reactjs debugging react-hooks

我试图直接从Material Ui(简单菜单https://material-ui.com/demos/menus/#menus)文档中使用此组件,以使菜单出现。但是,我在下面的当前尝试中遇到TypeError: react__WEBPACK_IMPORTED_MODULE_1___default.a.useState is not a function错误。我尝试过:

  • import React, { useState } from 'react';,然后在React内删除了const [anchorEl, setAnchorEl] = React.useState(null);,使其看起来像:const [anchorEl, setAnchorEl] = useState(null);
  • 我还尝试用数字替换null,但仍然遇到相同的错误。

注意:另一种尝试安装了正确的软件包并使我的package.json文件看起来像这样(TypeError dispatcher.useState is not a function when using React Hooks):

{
  "name": "speedy-react",
  "version": "0.1.0",
  "private": true,
  "dependencies": {
    "@material-ui/core": "^3.9.0",
    "@material-ui/icons": "^3.0.2",
    "classnames": "^2.2.6",
    "node-sass": "^4.11.0",
    "prop-types": "^15.6.2",
    "react": "16.7.0-alpha.0",
    "react-dom": "16.7.0-alpha.0",
    "react-test-renderer": "16.7.0-alpha.0",
    "react-scripts": "2.1.3"
  },
  "scripts": {
    "start": "react-scripts start",
    "build": "react-scripts build",
    "test": "react-scripts test",
    "eject": "react-scripts eject"
  },
  "eslintConfig": {
    "extends": "react-app"
  },
  "browserslist": [
    ">0.2%",
    "not dead",
    "not ie <= 11",
    "not op_mini all"
  ]
}

错误的屏幕截图:

enter image description here

我在做什么错,我该如何解决?

import React from 'react';
import Button from '@material-ui/core/Button';
import Menu from '@material-ui/core/Menu';
import MenuItem from '@material-ui/core/MenuItem';

const SimpleMenu = () => {
    const [anchorEl, setAnchorEl] = React.useState(null);

    function handleClick(event) {
        setAnchorEl(event.currentTarget);
    }

    function handleClose() {
        setAnchorEl(null);
    }

    return (
        <div>
            <Button
                aria-owns={anchorEl ? 'simple-menu' : undefined}
                aria-haspopup="true"
                onClick={handleClick}
            >
                Open Menu
            </Button>
            <Menu id="simple-menu" anchorEl={anchorEl} open={Boolean(anchorEl)} onClose={handleClose}>
                <MenuItem onClick={handleClose}>Profile</MenuItem>
                <MenuItem onClick={handleClose}>My account</MenuItem>
                <MenuItem onClick={handleClose}>Logout</MenuItem>
            </Menu>
        </div>
    );
};

export default SimpleMenu;

1 个答案:

答案 0 :(得分:0)

虽然我不确定上面的代码出了什么问题(我猜是使用非发行版的Material-ui,但据文档说明,导出未默认导出),但对于我来说,发生此错误的原因是不正确的进口。我的问题是我正在尝试

import someNonDefaultFunction from 'someModule';

在命名/非默认导入周围添加括号可以为我解决相同的错误消息:

import {someNonDefaultFunction} from 'someModule';