webpack中，有哪些常见的Plugin？他们分别是解决什么问题的？

[Cosen95]

[Cosen95]

plugin可以在webpack运行到某个时刻的时候，帮你做一些事情

HtmlWebpackPlugin

• HtmlWebpackPlugin会在打包结束后，自动生成一个html文件，并把打包生成的js自动引入到这个html文件中

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

module.exports = {
...
plugins: [
    new HtmlWebpackPlugin({
      template: 'src/index.html'
    }),
  ],
};

clean-webpack-plugin

• clean-webpack-plugin插件用来清除残留打包文件，特别是文件末尾添加了hash之后，会导致改变文件内容后重新打包时，文件名不同而内容越来越多。
• 新版本中的clean-webpack-plugin仅接受一个对象，默认不需要传任何参数。具体可参考https://blog.csdn.net/qq_23521659/article/details/88353708

const { CleanWebpackPlugin } = require('clean-webpack-plugin');

module.exports = {
...
plugins: [
    new CleanWebpackPlugin()
  ],
  output: {
    filename: 'bundle.js',
    path: path.resolve(__dirname, 'dist')
  }

SplitChunksPlugin

• 具体概念可参考https://juejin.im/post/5af15e895188256715479a9a

splitChunks: {
    chunks: "async",
    minSize: 30000,
    minChunks: 1,
    maxAsyncRequests: 5,
    maxInitialRequests: 3,
    automaticNameDelimiter: '~',
    name: true,
    cacheGroups: {
        vendors: {
            test: /[\\/]node_modules[\\/]/,
            priority: -10
        },
    default: {
            minChunks: 2,
            priority: -20,
            reuseExistingChunk: true
        }
    }
}

MiniCssExtractPlugin

• 将CSS提取为独立的文件的插件，对每个包含css的js文件都会创建一个CSS文件，支持按需加载css和sourceMap

const MiniCssExtractPlugin = require('mini-css-extract-plugin');
module.exports = {
  plugins: [
    new MiniCssExtractPlugin({
      // Options similar to the same options in webpackOptions.output
      // both options are optional
      filename: '[name].css',
      chunkFilename: '[id].css',
    }),
  ],
  module: {
    rules: [
      {
        test: /\.scss$/,
        use: [
          {
            loader: MiniCssExtractPlugin.loader
          },
          {
            loader: "css-loader",
            options: {
              importLoaders: 2 // 用于指定在 css-loader 前应用的 loader 的数量
              // modules: true   // 查询参数 modules 会启用 CSS 模块规范
            }
          },
          "sass-loader",
          "postcss-loader"
        ]
      },
      {
        test: /\.css$/,
        use: [
          {
            loader: MiniCssExtractPlugin.loader
          },
          "css-loader",
          "postcss-loader"
        ]
      }
    ],
  },
};

OptimizeCSSAssetsPlugin

• webpack5可能会内置CSS 压缩器，webpack4需要自己使用压缩器，可以使用 optimize-css-assets-webpack-plugin 插件。 设置 optimization.minimizer 覆盖webpack默认提供的，确保也指定一个JS压缩器

const UglifyJsPlugin = require('uglifyjs-webpack-plugin');
const MiniCssExtractPlugin = require('mini-css-extract-plugin');
const OptimizeCSSAssetsPlugin = require('optimize-css-assets-webpack-plugin');

module.exports = {
  optimization: {
    minimizer: [
      new UglifyJsPlugin({
        cache: true,
        parallel: true,
        sourcMap: true
      }),
      new OptimizeCSSAssetsPlugin({}),
    ],
  },
  plugins: [
    new MiniCssExtractPlugin({
      filename: "[name].css",
      chunkFilename: "[id].css"
    }),
  ],
  module: {
    rules: [
      {
        test: /\.css$/,
        use: [
          MiniCssExtractPlugin.loader,
          'css-loader'
        ]
      }
    ]
  }
}