const path = require('path');

module.exports = {
  mode: "production", // "production" | "development" | "none"  // 选择模式告诉webpack可以相应地使用它的内置优化{生产，开发}。
  entry: "./app/entry", // string | object | array  // defaults to ./src
  // Here the application starts executing
  // and webpack starts bundling
  output: {
    // options related to how webpack emits results
    path: path.resolve(__dirname, "dist"), // string
    // the target directory for all output files
    // must be an absolute path (use the Node.js path module)
    filename: "bundle.js", // string    // the filename template for entry chunks
    publicPath: "/assets/", // string    // the url to the output directory resolved relative to the HTML page
    library: "MyLibrary", // string,
    // the name of the exported library
    libraryTarget: "umd", // universal module definition    // the type of the exported library
    /* Advanced output configuration (click to show) */  },
  module: {
    // configuration regarding modules
    rules: [
      // rules for modules (configure loaders, parser options, etc.)
      {
        test: /\.jsx?$/,
        include: [
          path.resolve(__dirname, "app")
        ],
        exclude: [
          path.resolve(__dirname, "app/demo-files")
        ],
        // these are matching conditions, each accepting a regular expression or string
        // test and include have the same behavior, both must be matched
        // exclude must not be matched (takes preferrence over test and include)
        // Best practices:
        // - Use RegExp only in test and for filename matching
        // - Use arrays of absolute paths in include and exclude
        // - Try to avoid exclude and prefer include
        issuer: { test, include, exclude },
        // conditions for the issuer (the origin of the import)
        enforce: "pre",
        enforce: "post",
        // flags to apply these rules, even if they are overridden (advanced option)
        loader: "babel-loader",
        // the loader which should be applied, it'll be resolved relative to the context
        // -loader suffix is no longer optional in webpack2 for clarity reasons
        // see webpack 1 upgrade guide
        options: {
          presets: ["es2015"]
        },
        // options for the loader
      },
      {
        test: /\.html$/,
        use: [
          // apply multiple loaders and options
          "htmllint-loader",
          {
            loader: "html-loader",
            options: {
              /* ... */
            }
          }
        ]
      },
      { oneOf: [ /* rules */ ] },
      // only use one of these nested rules
      { rules: [ /* rules */ ] },
      // use all of these nested rules (combine with conditions to be useful)
      { resource: { and: [ /* conditions */ ] } },
      // matches only if all conditions are matched
      { resource: { or: [ /* conditions */ ] } },
      { resource: [ /* conditions */ ] },
      // matches if any condition is matched (default for arrays)
      { resource: { not: /* condition */ } }
      // matches if the condition is not matched
    ],
    /* Advanced module configuration (click to show) */  },
  resolve: {
    // options for resolving module requests
    // (does not apply to resolving to loaders)
    modules: [
      "node_modules",
      path.resolve(__dirname, "app")
    ],
    // directories where to look for modules
    extensions: [".js", ".json", ".jsx", ".css"],
    // extensions that are used
    alias: {
      // a list of module name aliases
      "module": "new-module",
      // alias "module" -> "new-module" and "module/path/file" -> "new-module/path/file"
      "only-module$": "new-module",
      // alias "only-module" -> "new-module", but not "only-module/path/file" -> "new-module/path/file"
      "module": path.resolve(__dirname, "app/third/module.js"),
      // alias "module" -> "./app/third/module.js" and "module/file" results in error
      // modules aliases are imported relative to the current context
    },
    /* alternative alias syntax (click to show) */    /* Advanced resolve configuration (click to show) */  },
  performance: {
    hints: "warning", // enum    maxAssetSize: 200000, // int (in bytes),
    maxEntrypointSize: 400000, // int (in bytes)
    assetFilter: function(assetFilename) {
      // Function predicate that provides asset filenames
      return assetFilename.endsWith('.css') || assetFilename.endsWith('.js');
    }
  },
  devtool: "source-map", // enum  // enhance debugging by adding meta info for the browser devtools
  // source-map most detailed at the expense of build speed.
  context: __dirname, // string (absolute path!)
  // the home directory for webpack
  // the entry and module.rules.loader option
  //   is resolved relative to this directory
  target: "web", // enum  // the environment in which the bundle should run
  // changes chunk loading behavior and available modules
  externals: ["react", /^@angular\//],  // Don't follow/bundle these modules, but request them at runtime from the environment
  serve: { //object
    port: 1337,
    content './dist',
    // ...
  },
  // lets you provide options for webpack-serve
  stats: "errors-only",  // lets you precisely control what bundle information gets displayed
  devServer: {
    proxy: { // proxy URLs to backend development server
      '/api': 'http://localhost:3000'
    },
    contentBase: path.join(__dirname, 'public'), // boolean | string | array, static file location
    compress: true, // enable gzip compression
    historyApiFallback: true, // true for index.html upon 404, object for multiple paths
    hot: true, // hot module replacement. Depends on HotModuleReplacementPlugin
    https: false, // true for self-signed, object for cert authority
    noInfo: true, // only errors & warns on hot reload
    // ...
  },
  plugins: [
    // ...
  ],
  // list of additional plugins
  /* Advanced configuration (click to show) */}