650 webpack 搭建本地服务器：watch，webpack-dev-server，HMR，publicPath、contentBase，hotOnly，host，port、open、compress，Proxy，changeOrigin，resolve解析，extensions、alias

为什么要搭建本地服务器？

---

Webpack watch

---

webpack-dev-server

• cnpm install --save-dev webpack-dev-server
• 注意，脚本是 "serve": "webpack serve"

---

webpack-dev-middleware 【了解】

---

webpack-dev-middleware的使用

---

认识模块热替换（HMR）

---

开启HMR

---

框架的HMR

---

React的HMR

• cnpm install -D @pmmmwh/react-refresh-webpack-plugin react-refresh

---

Vue的HMR

• cnpm install vue-loader vue-template-compiler -D

---

HMR的原理

---

HMR的原理图

---

webpack.config.js

const path = require('path');
const HtmlWebpackPlugin = require('html-webpack-plugin');
const ReactRefreshWebpackPlugin = require('@pmmmwh/react-refresh-webpack-plugin');
const VueLoaderPlugin = require('vue-loader/lib/plugin');

module.exports = {
  // watch: true,
  mode: "development",
  entry: "./src/index.js",
  output: {
    filename: "bundle.js",
    path: path.resolve(__dirname, "./build")
  },
  // 专门为webpack-dev-server配置
  devServer: {
    hot: true
  },
  module: {
    rules: [
      {
        test: /.jsx?$/i,
        use: "babel-loader"
      },
      {
        test: /.vue$/i,
        use: "vue-loader"
      },
      {
        test: /.css/i,
        use: [
          "style-loader",
          "css-loader"
        ]
      }
    ]
  },
  plugins: [
    new HtmlWebpackPlugin({
      template: "./index.html"
    }),
    new ReactRefreshWebpackPlugin(),
    new VueLoaderPlugin()
  ]
}

---

package.json

{
  "name": "webpack_devserver",
  "version": "1.0.0",
  "description": "",
  "main": "index.js",
  "scripts": {
    "build": "webpack",
    "watch": "webpack --watch",
    "serve": "webpack serve"
  },
  "author": "",
  "license": "ISC",
  "devDependencies": {
    "@babel/core": "^7.12.17",
    "@babel/preset-env": "^7.12.17",
    "@babel/preset-react": "^7.12.13",
    "@pmmmwh/react-refresh-webpack-plugin": "^0.4.3",
    "babel-loader": "^8.2.2",
    "css-loader": "^5.0.2",
    "html-webpack-plugin": "^5.2.0",
    "react-refresh": "^0.9.0",
    "style-loader": "^2.0.0",
    "vue-loader": "^15.9.6",
    "vue-template-compiler": "^2.6.12",
    "webpack": "^5.23.0",
    "webpack-cli": "^4.5.0",
    "webpack-dev-server": "^3.11.2"
  },
  "dependencies": {
    "express": "^4.17.1",
    "react": "^17.0.1",
    "react-dom": "^17.0.1",
    "vue": "^2.6.12",
    "webpack-dev-middleware": "^4.1.0"
  }
}

---

index.js

/**
 * 存在的问题:
 *  问题一: 每次修改源代码之后, 我们都需要重新执行npm run build
 *    * 通过watch监听源代码的变化
 * 
 * 目前的开发模式: 
 *    1.watch方案来监听文件的变化 
 *    2.通过live-server插件提供本地服务(当文件变化时,自动刷新页面)
 * 效率并不是特别高:
 *    1.对所有的源代码都重新进行编译
 *    2.编译成功后,都会生成新的文件(文件操作 file system)
 *    3.live-server属于VSCode插件(vim/webstorm) -> 不属于webpack给我们的解决方案
 *    4.live-server每次都会重新刷新整个页面
 * 
 *  webpack-dev-server: hot module replacement(HMR)
 */

import "./math";
import React from 'react';
import ReactDom from 'react-dom';
import ReactApp from './App.jsx';

import Vue from 'vue';
import VueApp from './App.vue';

console.log("Hello 哈哈哈");
console.log("abc");

// 【module是全局对象。】
if (module.hot) {
  module.hot.accept("./math.js", () => {
    console.log("math模块发生了更新~");
  });
}

// React的代码
ReactDom.render(<ReactApp/>, document.getElementById("app"));

// Vue的代码
new Vue({
  render: h => h(VueApp)
}).$mount("#root");

---

App.vue

<template>
  <div id="app">
    <h2 class="title">{{ message }}</h2>
  </div>
</template>

<script>
  export default {
    data() {
      return {
        message: "Hello 哈哈哈",
      };
    },
  };
</script>

<style scoped>
  .title {
    color: blue;
  }
</style>

---

App.jsx

import React, { Component } from "react";

class App extends Component {
  constructor(props) {
    super(props);

    this.state = {
      message: "Hello React",
    };
  }

  render() {
    return (
      <div>
        <h2>{this.state.message}</h2>
      </div>
    );
  }
}

export default App;

---

babel.config.js

module.exports = {
  presets: [
    ["@babel/preset-env"],
    ["@babel/preset-react"],
  ],
  plugins: [
    ["react-refresh/babel"]
  ]
}

---

output的publicPath

---

devServer的publicPath

---

devServer的contentBase

---

hotOnly、host配置

---

port、open、compress

---

---

Proxy代理

---

changeOrigin的解析

---

historyApiFallback

---

resolve模块解析

---

确实文件还是文件夹

---

extensions和alias配置

---

目录结构

---

webpack.config.js

const path = require('path');
const HtmlWebpackPlugin = require('html-webpack-plugin');
const ReactRefreshWebpackPlugin = require('@pmmmwh/react-refresh-webpack-plugin');
const VueLoaderPlugin = require('vue-loader/lib/plugin');

module.exports = {
  // watch: true,
  mode: "development",
  entry: "./src/index.js",
  output: {
    filename: "bundle.js",
    // 打包后的文件的输出目录
    path: path.resolve(__dirname, "./build"),
    // publicPath：在打包之后的静态资源前面进行一个路径的拼接，默认值是一个空字符串 【拼接：主机名 + publicPath + bundle.js】
    // js/bundle 会拼接成 -> ./js/bundle.js，通过相对路径访问
    // publicPath: "./"
    // publicPath: "/abc"
  },
  // 专门为webpack-dev-server
  // devServer为开发过程中, 开启一个本地服务
  devServer: {
    hot: true,
    hotOnly: true,
    // host: "0.0.0.0", // 经测试，不能通过 http://0.0.0.0:端口/ 进行访问
    // port: 7777,
    // open: true,
    compress: true,
    // 通过src与进入的静态资源会去配置的contentBase中查找【本地服务的路径是在"./why"】
    contentBase: path.resolve(__dirname, "./why"),
    watchContentBase: true, // abc.js代码改变后，自动刷新浏览器
    // 开发环境中，devServer的publicPath 和 output的publicPath一致
    // publicPath: "/abc",
    proxy: {
      // "/why": "http://localhost:8888"
      "/why": {
        // 映射，"/why"相当于"http://localhost:8888"
        target: "http://localhost:8888", 
        pathRewrite: {
          "^/why": ""
        },
        secure: false, // 支持https
        changeOrigin: true // 如果服务器做了验证，就要设置为true
      }
    },
    // historyApiFallback: true
    historyApiFallback: {
      rewrites: [
        {from: /abc/, to: "/index.html"}
      ]
    }
  },
  resolve: {
    extensions: ['.wasm', '.mjs', '.js', '.json', '.jsx', '.ts', '.vue'],
    alias: {
      "@": path.resolve(__dirname, "./src"),
      "pages": path.resolve(__dirname, "./src/pages")
    }
  },
  module: {
    rules: [
      {
        test: /.jsx?$/i,
        use: "babel-loader"
      },
      {
        test: /.vue$/i,
        use: "vue-loader"
      },
      {
        test: /.css/i,
        use: [
          "style-loader",
          "css-loader"
        ]
      }
    ]
  },
  plugins: [
    new HtmlWebpackPlugin({
      template: "./index.html"
    }),
    new ReactRefreshWebpackPlugin(),
    new VueLoaderPlugin()
  ]
}

---

index.js

import axios from 'axios';

import React from 'react';
import ReactDom from 'react-dom';
import ReactApp from './App.jsx';

import Vue from 'vue';
import VueApp from './App.vue';

import "./math";

console.log("Hello Coderwhy");
console.log("abc");

if (module.hot) {
  module.hot.accept("./math.js", () => {
    console.log("math模块发生了更新~");
  });
}

// React的代码
ReactDom.render(<ReactApp/>, document.getElementById("app"));

// Vue的代码
new Vue({
  render: h => h(VueApp)
}).$mount("#root");

// axios网络请求
// changeOrigin的解析：--> 因为使用了代码，默认情况下它的值是 http://localhost:8080，服务器接收来源的时候，如果不去对它做额外的配置，服务器会认为这次请求的来源就是 http://localhost:8080。本来应该是target对应的 "http://localhost:8888"，但是做了代理，请求变成了http://localhost:8080。如果服务器没有对来源做校验，此时不会有问题。如果服务器为了防止通过代理的方式爬服务器的数据，做了校验，校验这次请求是不是在http://localhost:8888，发现是8080，不是8888，就不会返回数据，所以要改回成8888。用了第三方库，取代理服务器，把源换成target的值http://localhost:8888，服务器就会验证通过。
axios.get("http://localhost:8080/why/moment").then(res => {
  console.log(res);
}).catch(err => {
  console.log(err);
});

---

---