rollup.config.js

import pkg from "./package.json";
import json from "rollup-plugin-json";
import typescript from "typescript";
import typescriptRollup from "rollup-plugin-typescript2";
import babel from "rollup-plugin-babel";
import postcss from "rollup-plugin-postcss-modules";
import { eslint } from "rollup-plugin-eslint";
import del from "del";
import serve from 'rollup-plugin-serve';
import staticSite from 'rollup-plugin-static-site';
import livereload from 'rollup-plugin-livereload';
import autoprefixer from 'autoprefixer';
import { uglify } from "rollup-plugin-uglify";
import cssnano from 'cssnano';

const cleanUp = (options = {}) => {
  const {
    hook = 'buildStart',
    targets = ["build/**"],
    verbose = false,
    ...rest
  } = options;

  return {
    name: 'delete',
    [hook]: () => del(targets, rest).then((paths) => {
      if (verbose || rest.dryRun) {
        const message = rest.dryRun
          ? `Expected files and folders to be deleted: ${paths.length}`
          : `Deleted files and folders: ${paths.length}`

        console.log("clearing the build folder");
      }
    })
  }
}
export default {
	watch: process.env.NODE_ENV !== "production" ? {
		include: "src/**",
		exclude: "node_modules/**"
		// chokidar: {
        //     usePolling: true,
		// 	include: 'src/**/*.{ts|tsx}',
		// 	exclude: "node_modules/**"
        // }
	}: undefined,
	input: "src/index.ts",
	output: [{
		file: pkg.main,
		format: "umd",
		sourcemap: process.env.NODE_ENV !== "production",
		name: 'demo'
    }/*,{
		file: pkg.module,
		sourcemap: true,
		format: "es"
	}*/],
	external: [
		...Object.keys(pkg.dependencies || {}),
		...Object.keys(pkg.peerDependencies || {}),
	],
  	plugins: [
		cleanUp({ verbose: true }),
		json,
		eslint({
			include: ["src/**"],
			exclude: ['src/**/*.css'],
			throwOnError: process.env.NODE_ENV === "production"
		}),
		postcss({
			getJSON: (cssFileName, json, outputFileName) => {
				var path          = require('path');
				var cssName       = path.basename(cssFileName, '.css');
				var jsonFileName  = path.resolve('./build/' + cssName + '.json');
				fs.writeFileSync(jsonFileName, JSON.stringify(json));
			},
            extract: true,
            plugins: [
				autoprefixer(),
				process.env.NODE_ENV === "production" ? cssnano() : () => {}
			],
            writeDefinitions: true,
			modules: true
        }),
		typescriptRollup({
			typescript,
			"clean": true,
			"verbosity": 0,
			"abortOnError": process.env.NODE_ENV === "production",
			"check": true
		}),
		babel({
			exclude: 'node_modules/**',
			include: 'src/**',
		}),
		...(process.env.NODE_ENV === "production" ? [uglify()] : [
			staticSite({
				dir: 'example',
				moreStyles: ["/build/index.css"],
				template: {
					path: "static/index.html"
				}
			}),
			serve({
				open: true,
				openPage: '/example/',
				verbose: true,
				// contentBase: ['build', 'example'],
				contentBase: ['.'],
				host: 'localhost',
				port: 9000,
			}),
			livereload()
		])
	]
};