项目初始化

$ npm init

安装webpack

本次创建是基于webpack4

$ npm install --save-dev

新建webpack配置文件

在根目录创建build文件夹，添加一个js文件，命名为webpack.base.conf.js

// webpack.base.conf.js 文件
const path = require('path');
const DIST_PATH = path.resolve(__dirname, '../dist');
module.exports = {
        entry: {
            app: './app/index.js'
        },
        output: {
            filename: "js/bundle.js",
            path: DIST_PATH
        }
};

使用merge的方式来组织webpack基础配置和不同环境的配置

先安装webpack-merge：

$ npm install --save-dev webpack-merge

在build文件夹中再添加一个js文件，命名为 webpack.prod.conf.js

// webpack.prod.conf.js 文件
const merge = require('webpack-merge');
const baseWebpackConfig = require('./webpack.base.conf');
module.exports = merge(baseWebpackConfig, {
    mode: 'production'
});

在根目录下创建app目录，然后创建index.js文件

var element =document.getElementById('root');
element.innerHTML = 'hello, world!';

在根目录创建一个public文件夹，然后新建一个index.html文件

// index.html
<!DOCTYPE html>
<html lang="en">
  <head>
      <meta charset="UTF-8">
      <title>从零开始搭建react工程</title>
  </head>
  <body>
        <div id="root"></div>
        <script src="../dist/js/bundle.js"></script>
  </body>
</html>

当前项目目录树

  |- /app
    |- index.js
  |- /node_modules
  |- /public
    |- index.html
  |- /build
    |- webpack.base.conf.js
    |- webpack.prod.conf.js
  |- package.json
  |- package-lock.json

安装webpack-cli

webpack 4.0 版本之后的webpack，已经将webpack命令工具迁移到webpack-cli模块了,需要安装 webpack-cli

$ npm install --save-dev webpack-cli

package.json文件 scripts属性配置一个build命令

其值为：webpack --config build/webpack.prod.conf.js，以下是scripts的相关代码

// package.json
"scripts": {
    "build": "webpack --config build/webpack.prod.conf.js",
    "test": "echo \"Error: no test specified\" && exit 1"
},

安装React

$ npm install --save react react-dom

修改app目录下的index.js的代码

import React from "react";
import ReactDom from "react-dom";

ReactDom.render(
    <h1>hello, world!</h1>,
    document.getElementById("root")
);

注意 import 属于ES6规范，因此需要转译ES2015+的语法，安装并配置 babel 以及相关依赖

$ npm install --save-dev babel-loader babel-core babel-preset-env babel-preset-react

根目录创建.babelrc文件，配置presets.

{
  "presets": [
    [
      "env",
      {
        "targets": {
          "browsers": [
            "> 1%",
            "last 5 versions",
            "ie >= 8"
          ]
        }
      }
    ],
    "react"
  ]
}

修改webpack.base.conf.js文件

// webpack.base.conf.js
const path = require('path');
const APP_PATH = path.resolve(__dirname, '../app');
const DIST_PATH = path.resolve(__dirname, '../dist');
module.exports = {
    entry: {
        app: './app/index.js'
    },    
    output: {
        filename: 'js/bundle.js',
        path: DIST_PATH
    },
    module: {
        rules: [
            {
                test: /\.js?$/,
                use: "babel-loader",
                include: APP_PATH
            }
        ]
    }
};

运行 npm run build

添加插件

public下的index.html本该自动添加到dist目录，并且引用资源自动加载到该文件，通过html-webpack-plugin实现这一步

$ npm install html-webpack-plugin --save-dev

webpack.prod.conf.js中配置plugins属性

const merge = require('webpack-merge');
const baseWebpackConfig = require('./webpack.base.conf.js');
const HtmlWebpackPlugin = require('html-webpack-plugin');

module.exports = merge(baseWebpackConfig, {
    mode: 'production',
    plugins: [
        new HtmlWebpackPlugin({
            template: 'public/index.html',
            inject: 'body',
            minify: {
                removeComments: true,
                collapseWhitespace: true,
                removeAttributeQuotes: true
            },
        })
    ]
});

删除 index.html 中手动引入的 script 标签

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>从零开始搭建react工程</title>
</head>
<body>
    <div id="root"></div>
</body>
</html>

重新编译查看 npm run build 浏览器打开查看目录 dist 下的 index.html

以上步骤都成功的前提下继续走下一步

生成的文件名添加Hash值，目的是解决缓存问题
修改webpack.prod.conf.js，mode: 'production', 增加以下代码

// webpack.prod.conf.js
output: {
    filename: "js/[name].[chunkhash:16].js",
},

生成前需要清理之前项目生成的文件，因为由于文件名的改变如果不删除会一直增加
安装插件 clean-webpack-plugin

$ npm install --save-dev clean-webpack-plugin

修改 webpack.prod.conf.js

// webpack.prod.conf.js
const merge = require('webpack-merge');
const baseWebpackConfig = require('./webpack.base.conf.js');
const HtmlWebpackPlugin = require('html-webpack-plugin');
const CleanWebpackPlugin = require('clean-webpack-plugin');

module.exports = merge(baseWebpackConfig, {
    mode: 'production',
    output: {
        filename: "js/[name].[chunkhash:16].js",
    },
    plugins: [
        new HtmlWebpackPlugin({
            template: 'public/index.html',
            inject: 'body',
            minify: {
                removeComments: true,
                collapseWhitespace: true,
                removeAttributeQuotes: true
            },
        }),
        new CleanWebpackPlugin(['../dist'], { allowExternal: true })
    ]
});

公共代码与业务代码分离

修改 webpack.base.conf.js 的 entry 入口属性，抽出框架代码

entry: {
      app: './app/index.js',
      framework: ['react','react-dom'],
},

修改webpack.prod.conf.js，增加以下代码，目的是分离框架代码和业务代码
虽然上面步骤抽出框架代码生成两个文件，但是app.js还是包含框架代码

optimization: {
        splitChunks: {
            chunks: "all",
            minChunks: 1,
            minSize: 0,
            cacheGroups: {
                framework: {
                    test: "framework",
                    name: "framework",
                    enforce: true
                }
            }
        }
    }

cacheGroups对象，定义了需要被抽离的模块
其中test属性是比较关键的一个值，他可以是一个字符串，也可以是正则表达式，还可以是函数。如果定义的是字符串，会匹配入口模块名称，会从其他模块中把包含这个模块的抽离出来
name是抽离后生成的名字，和入口文件模块名称相同，这样抽离出来的新生成的framework模块会覆盖被抽离的framework模块

整合 webpack-dev-server

开发环境开启服务监听文件改动实时更新最新内容

$ npm install --save-dev webpack-dev-server

在build中添加webpack.dev.conf.js文件

const path = require('path');
const merge = require('webpack-merge');
const baseWebpackConfig = require('./webpack.base.conf.js');
const HtmlWebpackPlugin = require('html-webpack-plugin');
const webpack = require('webpack');

module.exports = merge(baseWebpackConfig, {
    mode: 'development',
    output: {
        filename: "js/[name].[hash:16].js",
    },
    plugins: [
        new HtmlWebpackPlugin({
            template: 'public/index.html',
            inject: 'body',
            minify: {
                html5: true
            },
            hash: false
        }),
        new webpack.HotModuleReplacementPlugin()
    ],
    devServer: {
        port: '8080',
        contentBase: path.join(__dirname, '../public'),
        compress: true,
        historyApiFallback: true,
        hot: true,
        https: false,
        noInfo: true,
        open: true,
        proxy: {}
    }
});

在package.json scripts属性添加内容

"dev": "webpack-dev-server --inline --progress --config build/webpack.dev.conf.js",

npm run dev
自动打开浏览器打开入口页面实时更新

独立导出 css 文件

安装css相关依赖
sass less 预处理

$ npm install extract-text-webpack-plugin
$ npm install style-loader css-loader postcss-loader autoprefixer --save-dev
$ npm install less sass less-loader sass-loader stylus-loader node-sass --save-dev

webpack.base.conf.js 文件修改

// webpack.base.conf.js
{
    test: /\.css$/,
    use: [
        {
          loader: "style-loader" //在html中插入<style>标签
         },
         {
             loader: "css-loader",//获取引用资源，如@import,url()
         },
         {
              loader: "postcss-loader",
              options: {
                    plugins:[
                       require('autoprefixer')({
                           browsers:['last 5 version']
                       })
                  ]
              }
        }
     ]
},
{
   test:/\.less$/,
   use: [
         {  loader: "style-loader"  },
         {  loader: "css-loader" },
         {
            loader: "postcss-loader",//自动加前缀
            options: {
                   plugins:[
                          require('autoprefixer')({
                              browsers:['last 5 version']
                          })
                  ]
            }
         },
         {  loader: "less-loader" }
     ]
},
{
      test:/\.scss$/,
      use:[
             {  loader: "style-loader"  },
             {
                      loader: "css-loader",
             },
             {  loader: "sass-loader" },
             {
               loader: "postcss-loader",
              options: {
                    plugins:[
                         require('autoprefixer')({
                           browsers:['last 5 version']
                         })
                   ]
              }
          }
     ]
},

图片和路径处理

$ npm i file-loader url-loader --save-dev

webpack.base.conf.js 文件修改

// webpack.base.conf.js
{
    test: /\.(png|jpg|gif|woff|svg|eot|woff2|tff)$/,
    use: 'url-loader?limit=8129', 
    //注意后面那个limit的参数，当你图片大小小于这个限制的时候，会自动启用base64编码图片
    exclude: /node_modules/
}

build 时报错

Error: Chunk.entrypoints: Use Chunks.groupsIterable and filter by instanceof Entrypoint instead
    at Chunk.get (F:\react\createApp\node_modules\webpack\lib\Chunk.js:824:9)

webpack4.0中使用“extract-text-webpack-plugin”报错
解决办法

$ npm install extract-text-webpack-plugin@next

背景图片路径问题

由于css文件分离出来的原因，会导致在css文件夹下找images文件夹下的图片
解决办法 publicPath属性改为 '/'，以绝对路径的方式寻找资源

{
    test:/\.(png|jpg|gif)$/,
    use:[{
        loader:'url-loader',
        options: {
              // outputPath:'../',//输出**文件夹
              publicPath: '/',
              name: "images/[name].[ext]",
              limit:500  //是把小于500B的文件打成Base64的格式，写入JS
         }
      }]
},