23.oneOf

const { resolve } = require('path')
const HtmlWebpackPlugin = require('html-webpack-plugin')
// 提取css为单独文件
const MiniCssExtractPlugin = require('mini-css-extract-plugin')
// 压缩css
const OptimizeCssAssetsWebpackPlugin = require('optimize-css-assets-webpack-plugin')

// 定义nodejs环境变量：决定使用browserslist的哪个环境
process.env.NODE_ENV = 'production';

// 复用loader
const commonCssLoader = [
  {
    loader: MiniCssExtractPlugin.loader,
    options: {
      publicPath: '/',
    }
  },
  {
    loader: 'css-loader'
  },
  {
    // 还需要在package.json中定义browserslist
    loader: 'postcss-loader',
    options: {
      ident: 'postcss',
      plugins: () => [
        require('postcss-preset-env')()
      ]
    }
  }
]

module.exports = {
  entry: "./src/js/index.js",
  output: {
    filename: 'js/built.js',
    path: resolve(__dirname, 'build')
  },
  module: {
    rules: [
      {
        // 在package.json中eslintConfig --> airbnb
        test: /\.js/,
        exclude: /node_modules/,
        // 优先执行
        enforce: 'pre',
        use: [
          {
            loader: 'eslint-loader',
            options: {
              // 自动修复eslint的错误
              fix: true
            }
          }
        ]
      },
      {
        oneOf: [
          // 以下loader只会匹配一个
          // 注意：不能有两个配置处理同一种类型文件
          {
            test: /\.css$/,
            use: [
              // 'style-loader',
              ...commonCssLoader
            ]
          },
          {
            test: /\.less$/,
            use: [
              ...commonCssLoader,
              'less-loader'
            ]
          },
          {
            test: /\.(jpg|png|gif)$/,
            use: [
              {
                loader: 'url-loader',
                options: {
                  name: '[hash:10].[ext]',
                  limit: 8 * 1024,
                  esModule: false,
                  outputPath: 'imgs'
                }
              }
            ],
          },
          {
            exclude: /\.(js|html|css|less|jpg|png|gif)/,
            use: [
              {
                loader: 'file-loader',
                options: {
                  name: '[hash:10].[ext]',
                  outputPath: 'media'
                }
              }
            ],

          },
          {
            test: /\.html$/,
            use: ['html-loader']
          },
          /*
            正常来讲，一个文件只能被一个loader处理。
            当一个文件要被多个loader处理，那么一定要指定loader执行的先后顺序：
              先执行eslint 在执行babel
          */
          {
            test: /\.js/,
            use: [
              {
                loader: 'babel-loader',
                options: {
                  presets: [
                    [
                      '@babel/preset-env',
                      {
                        useBuiltIns: 'usage',
                        corejs: {
                          version: 3
                        },
                        targets: {
                          chrome: '60',
                          firefox: '60',
                          ie: '9',
                          safari: '10',
                          edge: '17'
                        }
                      }
                    ]
                  ]
                }
              }
            ]
          }
        ]
      }
    ]
  },
  plugins: [
    new HtmlWebpackPlugin({
      template: './src/index.html',
      minify: {
        collapseWhitespace: true,
        removeComments: true
      }
    }),
    new MiniCssExtractPlugin({
      // 对输出的css文件进行重命名
      filename: 'css/built.css'
    }),
    new OptimizeCssAssetsWebpackPlugin()
  ],
  mode: 'production'
}