rollup.config.js

import autoprefixer from 'autoprefixer';

import svelte from 'rollup-plugin-svelte';
import resolve from '@rollup/plugin-node-resolve';
import commonjs from '@rollup/plugin-commonjs';
import livereload from 'rollup-plugin-livereload';
import { terser } from 'rollup-plugin-terser';
import css from 'rollup-plugin-css-only';

import preprocess from 'svelte-preprocess';

const preprocessOptions = {
  postcss: {
    plugins: [
      autoprefixer,
    ],
  },
};
const production = !process.env.ROLLUP_WATCH;

const config = production
  ? ({
    input: 'src/index.js',
    output: [
      {
        file: 'build/bundle.mjs',
        format: 'es',
      },
      {
        file: 'build/bundle.js',
        format: 'umd',
        exports: 'named',
        name: 'Notifications',
      },
    ],
    plugins: [
      css({
        output: 'bundle.css',
      }),
      svelte({
        preprocess: preprocess(preprocessOptions),
        compilerOptions: {
          dev: !production,
        },
      }),
      resolve({
        browser: true,
        dedupe: ['svelte'],
      }),
      terser(),
    ],
  })
  : ({
    input: 'example/index.js',
    output: {
      sourcemap: true,
      format: 'iife',
      name: 'app',
      file: 'public/bundle.js',
    },
    plugins: [
      css({
        output: 'bundle.css',
      }),
      svelte({
        preprocess: preprocess(preprocessOptions),
        compilerOptions: {
          dev: !production,
        },
      }),
      resolve(),
      commonjs(),
      livereload('public'),
    ],
  });

export default config;