学习webpack4 - 基础配置
学习webpack4 - HTML处理
学习webpack4 - 样式处理
学习webpack4 - ES6语法转化
学习webpack4 - 第三方库的使用
学习webpack4 - 抽离公共代码

...持续中

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ES6语法转化

注意：开始之前以下内容之前，需要配置一些webpack的基础配置，传送门：学习webpack4.x - 基础配置

当前目录结构为：

• index.js 文件内容：

require('./index.css');
require('./index.scss');

• webpack.config.js文件内容：

let path = require('path');
let HtmlWebpackPlugin = require('html-webpack-plugin');
let MiniCssExtractPlugin = require('mini-css-extract-plugin'); //抽离CSS
let OptimizeCssPlugin = require('optimize-css-assets-webpack-plugin'); //优化项，比如压缩css等
let UglifyJsPlugin = require('uglifyjs-webpack-plugin'); //压缩js

module.exports = {
  // mode: 'development',

  //优化项配置
  optimization: {
    minimizer: [
      new OptimizeCssPlugin(),
      new UglifyJsPlugin({
        cache: true, //缓存
        parallel: true, //并发打包
        sourceMap: true //源码映射便于调试
      })
    ]
  },

  //开一个本地服务
  devServer: {
    port: 3000, //端口号
    progress: true, //进度条
    contentBase: './dist', //指定目录运行服务
    open: true //自动打开浏览器
  },
  entry: './src/index.js',
  output: {
    filename: 'bundle.js',
    path: path.resolve(__dirname, 'dist')
  },

  // 模块配置
  module: {
    rules: [{
      test: /\.(css|scss)$/,
      use: [MiniCssExtractPlugin.loader, 'css-loader', 'postcss-loader', 'sass-loader']
    }]
  },

  //插件配置
  plugins: [
    new HtmlWebpackPlugin({
      template: './src/index.html', //原始文件
      filename: 'index.html', //打包后的文件名称
      hash: true, //hash
    }),
    new MiniCssExtractPlugin({
      filename: 'main.css' //抽离出的css文件名称
    })
  ]
}

• package.json文件内容：

{
  "name": "webpack",
  "version": "1.0.0",
  "main": "index.js",
  "license": "MIT",
  "scripts": {
    "dev": "webpack --mode development && webpack-dev-server",
    "build": "webpack --mode production"
  },
  "devDependencies": {
    "autoprefixer": "^9.4.7",
    "css-loader": "^2.1.0",
    "html-webpack-plugin": "^3.2.0",
    "less": "^3.9.0",
    "less-loader": "^4.1.0",
    "mini-css-extract-plugin": "^0.5.0",
    "node-sass": "^4.11.0",
    "optimize-css-assets-webpack-plugin": "^5.0.1",
    "postcss-loader": "^3.0.0",
    "sass-loader": "^7.1.0",
    "style-loader": "^0.23.1",
    "uglifyjs-webpack-plugin": "^2.1.1",
    "webpack": "^4.29.4",
    "webpack-cli": "^3.2.3",
    "webpack-dev-server": "^3.1.14",
    "webpack-html-plugin": "^0.1.1"
  }
}

将ES6转化为ES5

step1: 打开src/index.js，输入：

const fn = () => {
  console.log('丸子');
}

fn ();

step2: 配置webpack.config.js文件：

将ES6转成ES5，需要babel-loader，配置规则为：

module.exports = {
  //...
  module: {
    //...
    {
      test: /\.js$/,
      use: {
        loader: 'babel-loader',
        options: {
          presets: ['@babel/preset-env'] // 根据目标浏览器自动转换为相应es5代码
        }
      }
    }
  }
};

step3: 安装插件：

yarn add babel-loader @babel/core @babel/preset-env -D

尝试运行： npm run dev, 成功！如下图：