rollup.config.js

import resolve from "rollup-plugin-node-resolve";
import babel from "rollup-plugin-babel";
import flow from "rollup-plugin-flow";
import commonjs from "rollup-plugin-commonjs";
import { uglify } from "rollup-plugin-uglify";
import replace from "rollup-plugin-replace";
import pkg from "./package.json";

const makeExternalPredicate = externalArr => {
  if (externalArr.length === 0) {
    return () => false;
  }
  const pattern = new RegExp(`^(${externalArr.join("|")})($|/)`);
  return id => pattern.test(id);
};

const minify = process.env.MINIFY;
const format = process.env.FORMAT;
const es = format === "es";
const umd = format === "umd";
const cjs = format === "cjs";

let output;

if (es) {
  output = { file: `dist/lru-memoize.es.js`, format: "es" };
} else if (umd) {
  if (minify) {
    output = {
      file: `dist/lru-memoize.umd.min.js`,
      format: "umd"
    };
  } else {
    output = { file: `dist/lru-memoize.umd.js`, format: "umd" };
  }
} else if (cjs) {
  output = { file: `dist/lru-memoize.cjs.js`, format: "cjs" };
} else if (format) {
  throw new Error(`invalid format specified: "${format}".`);
} else {
  throw new Error("no format specified. --environment FORMAT:xxx");
}

export default {
  input: "src/index.js",
  output: Object.assign(
    {
      name: "lru-memoize",
      exports: "named"
    },
    output
  ),
  external: makeExternalPredicate(
    umd
      ? Object.keys(pkg.peerDependencies || {})
      : [
          ...Object.keys(pkg.dependencies || {}),
          ...Object.keys(pkg.peerDependencies || {})
        ]
  ),
  plugins: [
    resolve({ jsnext: true, main: true }),
    flow(),
    commonjs({ include: "node_modules/**" }),
    babel({
      exclude: "node_modules/**",
      babelrc: false,
      runtimeHelpers: true,
      presets: [
        [
          "@babel/preset-env",
          {
            modules: false,
            loose: true
          }
        ],
        "@babel/preset-flow"
      ],
      plugins: [
        ["@babel/plugin-transform-runtime", { useESModules: !cjs }],
        "@babel/plugin-transform-flow-strip-types",
        "@babel/plugin-syntax-dynamic-import",
        "@babel/plugin-syntax-import-meta",
        "@babel/plugin-proposal-class-properties",
        "@babel/plugin-proposal-json-strings",
        [
          "@babel/plugin-proposal-decorators",
          {
            legacy: true
          }
        ],
        "@babel/plugin-proposal-function-sent",
        "@babel/plugin-proposal-export-namespace-from",
        "@babel/plugin-proposal-numeric-separator",
        "@babel/plugin-proposal-throw-expressions"
      ]
    }),
    umd || es
      ? replace({
          "process.env.NODE_ENV": JSON.stringify(
            minify ? "production" : "development"
          )
        })
      : null,
    minify ? uglify() : null
  ].filter(Boolean)
};