Webpack 常规配置

用 webpack 创建项目后，我们需要对 Webpack 进行配置来支持更复杂的业务要求。
1、Webpack 配置支持 ie，新增 .browserslistrc 文件

// .browserslistrc
[production]
> 1%
ie 9
[modern]
last 1 chrome version
last 1 firefox version
[ssr]
node 12

2、让 Webpack 支持 JSX、JS、TS、TSX，加入 ESLint 检查，支持 SASS。node 依赖单独打包，支持多页面，合并共用文件。

const ESLintWebpackPlugin = require('eslint-webpack-plugin')
const path = require('path')
const MiniCssExtractPlugin = require('mini-css-extract-plugin')
const HtmlWebpackPlugin = require('html-webpack-plugin')
const mode = 'production'
module.exports = {
  mode,
  // 多页面
  entry: {
    main: './src/index.js',
    admin: './src/admin.js',
    obb: './src/obb.js'
  },
  resolve: {
    alias: {
      '@': path.resolve(__dirname, './src/')
    },
    extensions: ['.ts', '.js', '.jsx','.tsx'],
  },
  plugins: [
    new ESLintWebpackPlugin({
      // 增加什么后缀就检查什么文件
      extensions: ['.js', '.jsx', '.ts', '.tsx']
    }),
    // build 后分离出 css 文件
    mode === 'production' && new MiniCssExtractPlugin({
      filename: '[name].[contenthash].css'
    }),
    // build 后分离出 html 文件
    new HtmlWebpackPlugin({
      filename: 'index.html',
      chunks: ['index']
    }),
    new HtmlWebpackPlugin({
      filename: 'admin.html',
      chunks: ['admin']
    }),
    new HtmlWebpackPlugin({
      filename: 'obb.html',
      chunks: ['obb']
    })
  ].filter(Boolean),
  // build 后的 js 文件 hash 重命名
  output: {
    filename: '[name].[contenthash].js'
  },
  // 优化运行时配置
  optimization: {
    // 运行时runtime文件(webpack配置)单独打包, index.js 不变则不会生成新的 main.js,只更新 runtime.js,节省用户带宽。
    runtimeChunk: 'single',
    splitChunks: {
      cacheGroups: {
        vendor: {
          // 优先级
          priority: 10,
          minSize: 0, // 如果不写0，react 文件尺寸太小会被跳过
          test: /[\\/]node_modules[\\/]/,  // 为了匹配 node_modules
          name: 'vendors',  // 文件名
          chunks: "all"  // all 表示同步加载和异步加载，async 表示异步加载，initial 表示同步加载
          // 这三行的意思是把两种加载方式的来自 node_modules 目录文件打包为 vendors.xxx.js, vendors 是第三方的意思
        },
        // 多页面共用文件配置
        commons: {
          priority: 5,
          minSize: 0,
          // 共用文件被至少两个文件引用了
          minChunks: 2,
          chunks: "all",
          name: 'commons'
        }
      }
    }
  },
  module: {
    rules: [
      {
        test: /\.[jt]sx?$/,
        exclude: /(node_modules|bower_components)/,
        use: {
          loader: 'babel-loader',
          options: {
            presets: [
              ['@babel/preset-env'],
              ['@babel/preset-react', {runtime: 'classic'}],
              ['@babel/preset-typescript']
            ]
          }
        }
      },
      // webpack 配置 sass
      {
        test: /\.s[ac]ss$/i,
        use: [
          // css支持导出, 给 JS 读取
          mode === 'production' ? MiniCssExtractPlugin.loader : 'style-loader',
          {
            loader: 'css-loader',
            options: {
              modules: {
                compileType: 'icss'
              }
            }
          },
          {
            loader: "sass-loader",
            // sass 自动导入全局，不用每个文件写import scss
            options: {
              additionalData: `
                @import "~@/scss-vars.scss";
              `,
              sassOptions: {
                includePaths: [__dirname]
              }
            }
          }
        ]
      }
    ]
  }
}

3、加入 ESLint 检查文件。

// .eslintrc.js 
module.exports = {
  extends: ['react-app'],
  rules: {
    // 'react/jsx-users-react': [2],
    // 提示要在 jsx 里手动引入 React
    'react/react-in-jsx-scope': [2]
  },
  // 引入 TS 检查
  overrides: [{
    files: ['*.ts', '*.tsx'],
    parserOptions: {
      project: './tsconfig.json'
    },
    extends: ['airbnb-typescript'],
    rules: {
      '@/typescript-eslint/object-curly-spacing': [0],
      'import/prefer-default-export': [0]
    }
  }]
}

4、创建 tsconfig.json 文件并配置 TS

tsc --init

{
  "compilerOptions": {
    /* Visit https://aka.ms/tsconfig.json to read more about this file */
    /* Basic Options */
    // "incremental": true,                   /* Enable incremental compilation */
    "target": "es5",                          /* Specify ECMAScript target version: 'ES3' (default), 'ES5', 'ES2015', 'ES2016', 'ES2017', 'ES2018', 'ES2019', 'ES2020', or 'ESNEXT'. */
    "module": "commonjs",                     /* Specify module code generation: 'none', 'commonjs', 'amd', 'system', 'umd', 'es2015', 'es2020', or 'ESNext'. */
    // "lib": [],                             /* Specify library files to be included in the compilation. */
    // "allowJs": true,                       /* Allow javascript files to be compiled. */
    // "checkJs": true,                       /* Report errors in .js files. */
    "jsx": "react",                           /* Specify JSX code generation: 'preserve', 'react-native', or 'react'. */
    // "declaration": true,                   /* Generates corresponding '.d.ts' file. */
    // "declarationMap": true,                /* Generates a sourcemap for each corresponding '.d.ts' file. */
    // "sourceMap": true,                     /* Generates corresponding '.map' file. */
    // "outFile": "./",                       /* Concatenate and emit output to single file. */
    // "outDir": "./",                        /* Redirect output structure to the directory. */
    // "rootDir": "./",                       /* Specify the root directory of input files. Use to control the output directory structure with --outDir. */
    // "composite": true,                     /* Enable project compilation */
    // "tsBuildInfoFile": "./",               /* Specify file to store incremental compilation information */
    // "removeComments": true,                /* Do not emit comments to output. */
    // "noEmit": true,                        /* Do not emit outputs. */
    // "importHelpers": true,                 /* Import emit helpers from 'tslib'. */
    // "downlevelIteration": true,            /* Provide full support for iterables in 'for-of', spread, and destructuring when targeting 'ES5' or 'ES3'. */
    // "isolatedModules": true,               /* Transpile each file as a separate module (similar to 'ts.transpileModule'). */
    /* Strict Type-Checking Options */
    "strict": true,                           /* Enable all strict type-checking options. */
    "noImplicitAny": true,                 /* Raise error on expressions and declarations with an implied 'any' type. */
    // "strictNullChecks": true,              /* Enable strict null checks. */
    // "strictFunctionTypes": true,           /* Enable strict checking of function types. */
    // "strictBindCallApply": true,           /* Enable strict 'bind', 'call', and 'apply' methods on functions. */
    // "strictPropertyInitialization": true,  /* Enable strict checking of property initialization in classes. */
    // "noImplicitThis": true,                /* Raise error on 'this' expressions with an implied 'any' type. */
    // "alwaysStrict": true,                  /* Parse in strict mode and emit "use strict" for each source file. */
    /* Additional Checks */
    // "noUnusedLocals": true,                /* Report errors on unused locals. */
    // "noUnusedParameters": true,            /* Report errors on unused parameters. */
    // "noImplicitReturns": true,             /* Report error when not all code paths in function return a value. */
    // "noFallthroughCasesInSwitch": true,    /* Report errors for fallthrough cases in switch statement. */
    // "noUncheckedIndexedAccess": true,      /* Include 'undefined' in index signature results */
    /* Module Resolution Options */
    // "moduleResolution": "node",            /* Specify module resolution strategy: 'node' (Node.js) or 'classic' (TypeScript pre-1.6). */
    // "baseUrl": "./",                       /* Base directory to resolve non-absolute module names. */
    // "paths": {},                           /* A series of entries which re-map imports to lookup locations relative to the 'baseUrl'. */
    // "rootDirs": [],                        /* List of root folders whose combined content represents the structure of the project at runtime. */
    // "typeRoots": [],                       /* List of folders to include type definitions from. */
    // "types": [],                           /* Type declaration files to be included in compilation. */
    // "allowSyntheticDefaultImports": true,  /* Allow default imports from modules with no default export. This does not affect code emit, just typechecking. */
    "esModuleInterop": true,                  /* Enables emit interoperability between CommonJS and ES Modules via creation of namespace objects for all imports. Implies 'allowSyntheticDefaultImports'. */
    // "preserveSymlinks": true,              /* Do not resolve the real path of symlinks. */
    // "allowUmdGlobalAccess": true,          /* Allow accessing UMD globals from modules. */
    /* Source Map Options */
    // "sourceRoot": "",                      /* Specify the location where debugger should locate TypeScript files instead of source locations. */
    // "mapRoot": "",                         /* Specify the location where debugger should locate map files instead of generated locations. */
    // "inlineSourceMap": true,               /* Emit a single file with source maps instead of having a separate file. */
    // "inlineSources": true,                 /* Emit the source alongside the sourcemaps within a single file; requires '--inlineSourceMap' or '--sourceMap' to be set. */
    /* Experimental Options */
    // "experimentalDecorators": true,        /* Enables experimental support for ES7 decorators. */
    // "emitDecoratorMetadata": true,         /* Enables experimental support for emitting type metadata for decorators. */
    /* Advanced Options */
    "skipLibCheck": true,                     /* Skip type checking of declaration files. */
    "forceConsistentCasingInFileNames": true  /* Disallow inconsistently-cased references to the same file. */
  }
}