rollup.config.js

import babel from "rollup-plugin-babel";
import { uglify } from "rollup-plugin-uglify";
import replace from "rollup-plugin-replace";
import filesize from "rollup-plugin-filesize";

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 ensureArray = maybeArr =>
  Array.isArray(maybeArr) ? maybeArr : [maybeArr];

const createConfig = ({ output, min = false, env } = {}) => ({
  input: "src/index.js",
  output: ensureArray(output).map(format =>
    Object.assign({}, format, {
      name: "ReactColorExtractor",
      exports: "named",
      globals: {
        react: "React"
      }
    })
  ),
  external: makeExternalPredicate([
    ...Object.keys(pkg.dependencies || {}),
    ...Object.keys(pkg.peerDependencies || {})
  ]),
  plugins: [
    filesize(),
    babel({ plugins: ["external-helpers"] }),
    env && replace({ "process.env.NODE_ENV": JSON.stringify(env) }),
    min && uglify()
  ].filter(Boolean)
});

export default [
  createConfig({
    output: [
      { file: pkg.main, format: "cjs" },
      { file: pkg.module, format: "es" }
    ]
  }),
  createConfig({
    output: { file: pkg.unpkg, format: "umd" },
    env: "production",
    min: true
  })
];