webpack.config.js

const path = require("path")
const merge = require("lodash.merge")

const nodeBabel = {
  loader: "babel-loader",
  options: {
    presets: [
      [
        "env",
        { targets: { node: "current", browsers: "last 2 versions, ie >= 11" } }
      ]
    ],
    plugins: ["transform-runtime", "transform-decorators-legacy"]
  }
}

const browserBabel = {
  loader: "babel-loader",
  options: {
    presets: [["env", { targets: { browsers: "last 2 versions, ie >= 11" } }]],
    plugins: ["transform-runtime", "transform-decorators-legacy"]
  }
}

const defaultConfig = {
  devtool: "source-map",
  output: {
    path: __dirname,
    library: "arboris",
    libraryTarget: "umd",
    umdNamedDefine: true
  },
  externals: {
    "mobx-state-tree": "mobx-state-tree",
    "react-dom/server": "react-dom/server"
  },
  module: {
    rules: [
      {
        test: /(\.js)$/,
        exclude: /node_modules/,
        use: nodeBabel
      },
      {
        test: /src\/(\.js)$/,
        loader: "eslint-loader",
        exclude: /node_modules/
      }
    ]
  },
  resolve: {
    modules: [path.resolve("./node_modules"), path.resolve("./src")],
    extensions: [".json", ".js"]
  }
}

const makeConfig = function(entry, target) {
  const newConfig = merge({}, defaultConfig)
  newConfig.entry = `${__dirname}/src/${entry}.js`
  newConfig.target = target

  if (target === "node") {
    newConfig.output.filename = `lib/${entry}.js`
    newConfig.module.rules[0].use = nodeBabel
  } else {
    newConfig.output.filename = `lib/${entry}.${target}.js`
    newConfig.module.rules[0].use = browserBabel
  }

  return newConfig
}

module.exports = [
  makeConfig("index", "node"),
  makeConfig("index", "web"),
  makeConfig("track", "node"),
  makeConfig("track", "web")
]