const config = {
  // 定义入口
  entry: {
    app: path.join(__dirname, "app")
  },
  // 定义包体文件
  output: {
    // 输出目录
    path: path.join(__dirname, "build"),

    // 输出文件名
    filename: "[name].js"
    // 使用 hash 作为文件名
    // filename: "[name].[chunkhash].js",
  },
  // 定义如何处理
  module: {
    rules: [
      {
        test: /\.js$/,
        use: "babel-loader",
        exclude: /node_modules/
      }
    ]
  },
  // 添加额外插件操作
  plugins: [new webpack.DefinePlugin()]
};

module.exports = [{
  entry: './app.js',
  output: ...,
  ...
}, {
  entry: './app.js',
  output: ...,
  ...
}]

const config = {
  resolve: {
    alias: {
      /*...*/
    },
    extensions: [
      /*...*/
    ],
    modules: [
      /*...*/
    ]
  }
};

const config = {
  module: {
    rules: [
      {
        // **Conditions**
        test: /\.js$/, // Match files
        enforce: "pre", // "post" too

        // **Restrictions**
        include: path.join(__dirname, "app"),
        exclude: path => path.match(/node_modules/),

        // **Actions**
        use: "babel-loader"
      }
    ]
  }
};

// Process foo.png through url-loader and other matches
import "url-loader!./foo.png";

// Override possible higher level match completely
import "!!url-loader!./bar.png";

/******/ (function(modules) { // webpackBootstrap
...
/* 0 */
/***/ (function(module, __webpack_exports__, __webpack_require__) {

"use strict";
__webpack_require__.r(__webpack_exports__);
/* harmony default export */ __webpack_exports__["default"] = ((text = "Hello world") => {
  const element = document.createElement("div");

  element.innerHTML = text;

  return element;
});

/***/ })
/******/ ]);