Webpack + Babel 错误

Question

我正在尝试配置 webpack 并启动并运行所有内容，但现在遇到了同样的错误。我梳理了其他一些似乎已通过更正拼写/语法错误解决的帖子，但我似乎无法在我的代码中找出任何错误。有更严重的事情发生吗？

ERROR in ./src/components/App/App.js
Module parse failed: /Users/Desktop/fred/src/components/App/App.js Unexpected token (7:11)
You may need an appropriate loader to handle this file type.
| 
|   render() {
|         return (
|           <h1>Hello</h1>;
|         );
|     };
| 
@ ./src/index.js 3:0-39
@ multi (webpack)-dev-server/client?http://localhost:8080 webpack-dev-server/client?http://localhost:8080 webpack/hot/only-dev-server ./src/index

这是我的 webpack.config：

var path = require("path");
var webpack = require("webpack");
var autoprefixer = require('autoprefixer');
var precss = require('precss');

module.exports = {
  entry: [
    'webpack-dev-server/client?http://localhost:8080',
    'webpack/hot/only-dev-server',
    './src/index'
  ],
  output: {
    path: path.resolve(__dirname, 'build'),
    publicPath: '/build/',
    filename: "bundle.js"
  },
  resolve: {
    extensions: ['*', '.js', '.jsx', '.png', '.json']
  },
  plugins: [
    new webpack.HotModuleReplacementPlugin(),
    new webpack.NoErrorsPlugin(),
    new webpack.LoaderOptionsPlugin({
      options: {
        context: __dirname,
        postcss: [
          autoprefixer
        ]
      }
    })
  ],
  module: {
    loaders: [
      {
        test: /\.js?$/,
        exclude: /node_modules/,
        loaders: ['react-hot-loader', 'babel-loader']
      },
      {
        test: /\.jsx?$/,
        loaders: ['react-hot-loader', 'babel-loader']
      },
      {
        test: /\.scss$/,
        loaders: ['style-loader', 'css-loader', 'postcss-loader']
      },
      {
        test: /\.(png|jpg|jpeg|gif|svg|woff|woff2)$/,
        loader: 'url-loader?limit=10000',
      }
    ],
    rules: [
      {
        test: /\.css$/,
        use: [ 'style-loader', 'css-loader' ]
      }
    ]
  }
};

我的 App.js：

import React, { Component } from 'react';
import s from './App.scss';

class App extends Component {

  render() {
    return (
      <h1>Hello</h1>;
    );
  };

}

export default App;

我的 index.js：

import React from 'react';
import { render } from 'react-dom';
import App from './components/App/App';

let element = React.createElement(App, {});
render(element, document.querySelector('.container'));

我的.babelrc：

{
  "presets" : ["es2015", "react", "stage-0"]
}

还有我的 package.json：

{
  "name": "fred test",
  "version": "1.0.0",
  "description": "a fred test",
  "main": "index.js",
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1",
    "start": "webpack-dev-server"
  },
  "author": "fred",
  "license": "ISC",
  "devDependencies": {
    "autoprefixer": "^6.7.7",
    "babel-core": "^6.24.1",
    "babel-loader": "^6.4.1",
    "babel-preset-es2015": "^6.24.1",
    "babel-preset-react": "^6.24.1",
    "babel-preset-stage-0": "^6.24.1",
    "css-loader": "^0.28.0",
    "file-loader": "^0.11.1",
    "postcss": "^5.2.17",
    "postcss-loader": "^1.3.3",
    "precss": "^1.4.0",
    "react-hot-loader": "^1.3.1",
    "style-loader": "^0.16.1",
    "webpack": "^2.3.3",
    "webpack-dev-server": "^2.4.2"
  },
  "dependencies": {
    "normalize.css": "^6.0.0",
    "react": "^15.5.4",
    "react-dom": "^15.5.4"
  }
}

Answer 1

问题是您同时定义了module.rules 和module.loaders。只要存在module.rules，Webpack 就会完全忽略module.loaders（仅出于兼容性原因而存在）。在您的情况下，所有 JavaScript 规则都在 module.loaders 内，因此没有一个被使用。

要修复它，请将所有内容放入 module.rules。对于.js 文件还有两条规则，/\.js?$/ 匹配.j 和.js，因为? 表示出现一次或零次，同样/\.jsx?$/ 匹配.js 和.jsx，即你真正想要什么，而为.j 制定规则是没有意义的。

module: {
  rules: [
    {
      test: /\.jsx?$/,
      exclude: /node_modules/,
      loaders: ['react-hot-loader', 'babel-loader']
    },
    {
      test: /\.scss$/,
      loaders: ['style-loader', 'css-loader', 'postcss-loader']
    },
    {
      test: /\.(png|jpg|jpeg|gif|svg|woff|woff2)$/,
      loader: 'url-loader?limit=10000',
    },
    {
      test: /\.css$/,
      use: [ 'style-loader', 'css-loader' ]
    }
  ]
}

Answer 2

您使用的是 ES6 版本的 Javascript。你需要在 webpack 中预设配置来理解和转换它。

您可以尝试将以下内容添加到您的 webpack 模块配置中吗？

 loaders : [
      {
        test:/\.jsx?$/,
        exclude:/node_modules/,
        loader: 'babel-loader',
        query:{
          presets: ['es2015','react','stage-0']
        }
      },
      // ... 
   ]