rollup.config.js

import commonjs from "rollup-plugin-commonjs";
import livereload from "rollup-plugin-livereload";
import resolve from "rollup-plugin-node-resolve";
import svelte from "rollup-plugin-svelte";
import { terser } from "rollup-plugin-terser";
import pkg from "./package.json";

const dev = !!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: dev ? "dev/main.js" : "src/index.js",
  output: dev
    ? {
        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: [
    svelte({
      // enable run-time checks when not in production
      dev: dev,
      // we'll extract any component CSS out into
      // a separate file — better for performance
      css: css => {
        css.write("public/bundle.css");
      }
    }),

    // 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({
      browser: true,
      dedupe: importee =>
        importee === "svelte" || importee.startsWith("svelte/")
    }),
    commonjs({
      include: ["node_modules/**"]
    }),

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

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