在 Laravel 5.7 React 应用程序中，出现错误：“classProperties”当前未启用

我很新React.js。我安装了拉拉维尔 5.7并通过运行以下命令将 Vue.js 脚手架与 React 交换：

php artisan preset react

现在的问题是，我无法将任何内容分配给组件内的状态。

例如，如果我在组件内执行以下操作：

state = { foo: false };

我收到错误：

ERROR in ./resources/js/components/Root.js
Module build failed (from ./node_modules/babel-loader/lib/index.js):
SyntaxError: D:\xampp\htdocs\smart-school-v0.1\resources\js\components\Root.js: Support for the experimental syntax 'classProperties' isn't currently enabled (8:11):

我安装了：

@babel/plugin-proposal-class-properties

并更新了.babelrc（Babel 配置文件）是这样的：

{
  "presets": [
    "@babel/preset-env",
    "@babel/preset-react"
  ],
  "plugins": [
      "@babel/plugin-proposal-class-properties"
  ]
}

我跟着this https://github.com/babel/babel/issues/8577#issuecomment-439579410但没有运气。

包.json

{
    "private": true,

    "scripts": {
        "dev": "npm run development",
        "development": "cross-env NODE_ENV=development node_modules/webpack/bin/webpack.js --progress --hide-modules --config=node_modules/laravel-mix/setup/webpack.config.js",
        "watch": "npm run development -- --watch",
        "watch-poll": "npm run watch -- --watch-poll",
        "hot": "cross-env NODE_ENV=development node_modules/webpack-dev-server/bin/webpack-dev-server.js --inline --hot --config=node_modules/laravel-mix/setup/webpack.config.js",
        "prod": "npm run production",
        "production": "cross-env NODE_ENV=production node_modules/webpack/bin/webpack.js --no-progress --hide-modules --config=node_modules/laravel-mix/setup/webpack.config.js"
    },
    "devDependencies": {
        "@babel/plugin-proposal-class-properties": "^7.2.3",
        "@babel/preset-env": "^7.2.3",
        "@babel/preset-react": "^7.0.0",
        "axios": "^0.18",
        "babel-preset-react": "^6.23.0",
        "bootstrap": "^4.0.0",
        "cross-env": "^5.1",
        "jquery": "^3.2",
        "laravel-mix": "^4.0.13",
        "lodash": "^4.17.5",
        "popper.js": "^1.12",
        "react": "^16.2.0",
        "react-dom": "^16.2.0",
        "resolve-url-loader": "^2.3.1",
        "sass": "^1.15.3",
        "sass-loader": "^7.1.0"
    },
    "dependencies": {
        "react-router-dom": "^4.3.1"
    }
}

.babelrc

 {
    "presets": [
    "@babel/preset-env",
    "@babel/preset-react"
    ],
    "plugins": [
        "@babel/plugin-proposal-class-properties"
    ]
 }

Root.js 组件

import React, { Component } from 'react';
import ReactDOM from 'react-dom';

export default class Root extends Component {

    state = { foo: false };

    render() {

        return (
        <p>Loaded</p>
        );
    }
}

if (document.getElementById('app')) {
    ReactDOM.render(<Root />, document.getElementById('app'));
}

它没有按预期工作，我不断收到此错误：

Syntax Error: SyntaxError: D:\xampp\htdocs\smart-school-v0.1\resources\js\components\Root.js: Support for the experimental syntax 'classProperties' isn't currently enabled (19:11):

17 |
18 |
> 19 |     state = { foo: false };
    |           ^
20 |
21 |     render() {
22 |

Add @babel/plugin-proposal-class-properties (https://git.io/vb4SL) to the 'plugins' section of your Babel config to enable transformation.


@ ./resources/js/app.js 14:0-28
@ multi ./resources/js/app.js ./resources/sass/app.scss
                                                                                                                                                                                            Asset     Size   Chunks
    Chunk Names
/css/app.css  0 bytes  /js/app  [emitted]  /js/app
/js/app.js  593 KiB  /js/app  [emitted]  /js/app

ERROR in ./resources/js/components/Root.js
Module build failed (from ./node_modules/babel-loader/lib/index.js):
SyntaxError: D:\xampp\htdocs\smart-school-v0.1\resources\js\components\Root.js: Support for the experimental syntax 'classProperties' isn't currently enabled (19:11):

请帮帮我。

提前致谢。

1. 在根文件夹中创建 .babelrc 文件。

2. 在.babelrc中写入：

{ "plugins": ["@babel/plugin-proposal-class-properties"] }

3. 运行 npm install --save-dev @babel/plugin-proposal-class-properties

4. 运行 npm run dev

希望它能帮助你。