1、概念

webpack作为一个打包工具，通过给定的入口文件，通过loader等扫描手段，将不同的.js,.css,.scss等各种文件，压缩打包成一个指定位置的出口压缩js文件

2、基本目录结构

node_modules：为node安装模块
public: 存放一些公共文件或压缩后的源码
src: 存放一些源码
package.json: 一个项目的基本信息，及依赖包的管理
webpack.config.js：webpack的配置文件

3、package.json文件分析

{
  "name": "webpack-student",  //项目描述信息
  "version": "1.0.0",
  "description": "Sample wepack project",
  "scripts": {    //脚本命令，执行 npm start == webpack, npm run server == webpack-dev-server --open
    "start": "webpack",
    "server": "webpack-dev-server --open",
    "dev": "webpack --mode development",
    "build": "webpack --mode production"
  },
  "devDependencies": {  //开发环境
    "babel-core": "^6.26.3",
    "babel-loader": "^7.1.5",
    "babel-preset-es2015": "^6.24.1",
    "babel-preset-react": "^6.24.1",
    "css-loader": "^3.4.1",
    "extract-text-webpack-plugin": "^4.0.0-beta.0",
    "style-loader": "^1.1.2",
    "webpack": "^4.41.5",
    "webpack-cli": "^3.3.10",
    "webpack-dev-server": "^3.10.1"
  },
  "dependencies": {  //生产环境
    "babel-core": "^6.26.3",
    "babel-loader": "^7.1.5",
    "react": "^16.12.0",
    "react-dom": "^16.12.0",
    "uglifyjs-webpack-plugin": "^2.2.0"
  }
}

4、webpack.config.js文件描述

const webpack = require('webpack')
const ExtractTextPlugin = require('extract-text-webpack-plugin');
const UglifyJSPlugin = require('uglifyjs-webpack-plugin');

module.exports = {
    devtool: 'eval-source-ma', //代码调试工具
    entry: __dirname + "/src/main.js", //唯一入口文件，__dirname是node的一个全局变量，它指向当前执行脚本所在的目录
    output: {
        path: __dirname + "/public", //打包后存放的地方
        filename: "bundle.js" //打包后输出文件的文件名
    },
    devServer: {
        contentBase: "./public", //本地服务器加载页面所在的目录
        historyApiFallback: true, //不跳转，所有的跳转都指向index.html
        inline: true //源文件改动，实时刷新
    },
    module: {
        rules: [{
            test: /(\.js|\.jsx)$/,  //loader匹配规则
            use: {
                loader: "babel-loader",
                },
            // include: __dirname + '/src/',
            exclude: /node_modules/
        },
        {
            test:/\.css$/,
            use:[
                {
                    loader:"style-loader"
                },
                {
                    loader:"css-loader",
                    options:{
                        modules:true  //css模块化按钮
                    }
                }
            ]
        }
    ]
    },
    optimization: {
        minimizer: [
                 new UglifyJSPlugin({
                     uglifyOptions: {
                         output: {
                             comments: false
                         },
                         compress: {
                             warnings: false,
                             drop_debugger: true,
                             drop_console: true
                         }
                     }
                 }),
             ]
       },
    plugins:[   //插件
        new webpack.BannerPlugin('zxq实践编写'),
        new ExtractTextPlugin("style.css")
    ]
}