Webpack如何设置一个开发环境，开发会变得容易些呢？

开发环境

调整webpack.config.js

 const path = require('path');
 const HtmlWebpackPlugin = require('html-webpack-plugin');

 module.exports = {
+  mode: 'development',
   entry: {
     index: './src/index.js',
     print: './src/print.js',
   },
   plugins: [
     new HtmlWebpackPlugin({
-      title: 'Output Management',
+      title: 'Development',
     }),
   ],
   output: {
     filename: '[name].bundle.js',
     path: path.resolve(__dirname, 'dist'),
     clean: true,
   },
 };

使用 source map

调整webpack.config.js

 const path = require('path');
 const HtmlWebpackPlugin = require('html-webpack-plugin');

 module.exports = {
   mode: 'development',
   entry: {
     index: './src/index.js',
     print: './src/print.js',
   },
+  devtool: 'inline-source-map',
   plugins: [
     new HtmlWebpackPlugin({
       title: 'Development',
     }),
   ],
   output: {
     filename: '[name].bundle.js',
     path: path.resolve(__dirname, 'dist'),
     clean: true,
   },
 };

src/print.js

 export default function printMe() {
-  console.log('I get called from print.js!');
+  cosnole.log('I get called from print.js!');
 }

运行npm run build

...
[webpack-cli] Compilation finished
asset index.bundle.js 1.38 MiB [emitted] (name: index)
asset print.bundle.js 6.25 KiB [emitted] (name: print)
asset index.html 272 bytes [emitted]
runtime modules 1.9 KiB 9 modules
cacheable modules 530 KiB
  ./src/index.js 406 bytes [built] [code generated]
  ./src/print.js 83 bytes [built] [code generated]
  ./node_modules/lodash/lodash.js 530 KiB [built] [code generated]
webpack 5.4.0 compiled successfully in 706 ms

显示错误

Uncaught ReferenceError: cosnole is not defined
   at HTMLButtonElement.printMe (print.js:2)

选择一个开发工具

使用 watch mode(观察模式)

package.json

 {
   "name": "webpack-demo",
   "version": "1.0.0",
   "description": "",
   "private": true,
   "scripts": {
     "test": "echo \"Error: no test specified\" && exit 1",
+    "watch": "webpack --watch",
     "build": "webpack"
   },
   "keywords": [],
   "author": "",
   "license": "ISC",
   "devDependencies": {
     "html-webpack-plugin": "^4.5.0",
     "webpack": "^5.4.0",
     "webpack-cli": "^4.2.0"
   },
   "dependencies": {
     "lodash": "^4.17.20"
   }
 }

npm run watch 查看webpack如何编译

src/print.js(移除错误)

 export default function printMe() {
-  cosnole.log('I get called from print.js!');
+  console.log('I get called from print.js!');
 }

### 使用 webpack-dev-server

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

#### 修改配置文件 webpack.config.js

const path = require('path');
const HtmlWebpackPlugin = require('html-webpack-plugin');

module.exports = {
  mode: 'development',
  entry: {
    index: './src/index.js',
    print: './src/print.js',
  },
  devtool: 'inline-source-map',
+  devServer: {
+    static: './dist',
+  },
  plugins: [
    new HtmlWebpackPlugin({
      title: 'Development',
    }),
  ],
  output: {
    filename: '[name].bundle.js',
    path: path.resolve(__dirname, 'dist'),
    clean: true,
  },
+  optimization: {
+    runtimeChunk: 'single',
+  },
};

#### 调整 package.json

 {
  "name": "webpack-demo",
  "version": "1.0.0",
  "description": "",
  "private": true,
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1",
    "watch": "webpack --watch",
+    "start": "webpack serve --open",
    "build": "webpack"
  },
  "keywords": [],
  "author": "",
  "license": "ISC",
  "devDependencies": {
    "html-webpack-plugin": "^4.5.0",
    "webpack": "^5.4.0",
    "webpack-cli": "^4.2.0",
    "webpack-dev-server": "^3.11.0"
  },
  "dependencies": {
    "lodash": "^4.17.20"
  }
}

### 使用 webpack-dev-middleware

#### 安装 express 和 webpack-dev-middleware

npm install --save-dev express webpack-dev-middleware

#### 调整 webpack.config.js

 const path = require('path');
 const HtmlWebpackPlugin = require('html-webpack-plugin');

 module.exports = {
   mode: 'development',
   entry: {
     index: './src/index.js',
     print: './src/print.js',
   },
   devtool: 'inline-source-map',
   devServer: {
     static: './dist',
   },
   plugins: [
     new HtmlWebpackPlugin({
       title: 'Development',
     }),
   ],
   output: {
     filename: '[name].bundle.js',
     path: path.resolve(__dirname, 'dist'),
     clean: true,
    publicPath: '/',
   },
 };

项目目录(project)

  webpack-demo
  |- package.json
  |- package-lock.json
  |- webpack.config.js
+ |- server.js
  |- /dist
  |- /src
    |- index.js
    |- print.js
  |- /node_modules

server.js

const express = require('express');
const webpack = require('webpack');
const webpackDevMiddleware = require('webpack-dev-middleware');

const app = express();
const config = require('./webpack.config.js');
const compiler = webpack(config);

// 告知 express 使用 webpack-dev-middleware，
// 以及将 webpack.config.js 配置文件作为基础配置。
app.use(
  webpackDevMiddleware(compiler, {
    publicPath: config.output.publicPath,
  })
);

// 将文件 serve 到 port 3000。
app.listen(3000, function () {
  console.log('Example app listening on port 3000!\n');
});

package.json

 {
   "name": "webpack-demo",
   "version": "1.0.0",
   "description": "",
   "private": true,
   "scripts": {
     "test": "echo \"Error: no test specified\" && exit 1",
     "watch": "webpack --watch",
     "start": "webpack serve --open",
+    "server": "node server.js",
     "build": "webpack"
   },
   "keywords": [],
   "author": "",
   "license": "ISC",
   "devDependencies": {
     "express": "^4.17.1",
     "html-webpack-plugin": "^4.5.0",
     "webpack": "^5.4.0",
     "webpack-cli": "^4.2.0",
     "webpack-dev-middleware": "^4.0.2",
     "webpack-dev-server": "^3.11.0"
   },
   "dependencies": {
     "lodash": "^4.17.20"
   }
 }

npm run server

Example app listening on port 3000!
...
<i> [webpack-dev-middleware] asset index.bundle.js 1.38 MiB [emitted] (name: index)
<i> asset print.bundle.js 6.25 KiB [emitted] (name: print)
<i> asset index.html 274 bytes [emitted]
<i> runtime modules 1.9 KiB 9 modules
<i> cacheable modules 530 KiB
<i>   ./src/index.js 406 bytes [built] [code generated]
<i>   ./src/print.js 83 bytes [built] [code generated]
<i>   ./node_modules/lodash/lodash.js 530 KiB [built] [code generated]
<i> webpack 5.4.0 compiled successfully in 709 ms
<i> [webpack-dev-middleware] Compiled successfully.
<i> [webpack-dev-middleware] Compiling...
<i> [webpack-dev-middleware] assets by status 1.38 MiB [cached] 2 assets
<i> cached modules 530 KiB (javascript) 1.9 KiB (runtime) [cached] 12 modules
<i> webpack 5.4.0 compiled successfully in 19 ms
<i> [webpack-dev-middleware] Compiled successfully.