rollup.config.js

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 pkg from './package.json';
import autoPreprocess from 'svelte-preprocess';
import babel from 'rollup-plugin-babel';

const production = !process.env.ROLLUP_WATCH;
const name = pkg.name
  .replace(/^(@\S+\/)?(svelte-)?(\S+)/, '$3')
  .replace(/^\w/, (m) => m.toUpperCase())
  .replace(/-\w/g, (m) => m[1].toUpperCase());

export default {
  input: !production ? 'src/main.js' : 'src/Waypoint.svelte',
  output: !production
    ? {
      sourcemap: true,
      format: 'iife',
      name: 'app',
      file: 'public/bundle.js',
    }
    : [
      {
        file: pkg.module,
        format: 'es',
        sourcemap: true,
        name,
      },
      {
        file: pkg.main,
        format: 'umd',
        sourcemap: true,
        name,
      },
    ],
  plugins: [
    babel({
      runtimeHelpers: true,
    }),
    svelte({
      // enable run-time checks when not in production
      dev: !production,

      /**
       * Auto preprocess supported languages with
       * '<template>'/'external src files' support
       **/
      preprocess: autoPreprocess({
        postcss: true,
      }),
    }),

    // If you have external dependencies installed from
    // npm, you'll most likely need these plugins. In
    // some cases you'll need additional configuration —
    // consult the documentation for details:
    // https://github.com/rollup/rollup-plugin-commonjs
    resolve(),
    commonjs({
      include: ['node_modules/**'],
    }),

    // Watch the `public` directory and refresh the
    // browser on changes when not in production
    !production && livereload('public'),

    // If we're building for production (npm run build
    // instead of npm run dev), minify
    production && terser(),
  ],
  watch: {
    clearScreen: false,
  },
};