rollup.config.mjs

import resolve from '@rollup/plugin-node-resolve';
import commonjs from '@rollup/plugin-commonjs';
import babel from '@rollup/plugin-babel';
import terser from '@rollup/plugin-terser';
import sourceMaps from 'rollup-plugin-sourcemaps';
import { readFileSync } from 'node:fs';

const pkg = JSON.parse(readFileSync('./package.json'));

const extensions = ['.js', '.mjs'];

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

const external = [
    ...Object.keys(pkg.dependencies || {}),
    ...Object.keys(pkg.peerDependencies || {}),
];

const appendMin = (file) => file.replace(/(\.[\w\d_-]+)$/i, '.min$1');
const replaceFilename = (file, name) =>
    file.replace(/(.*)\/.*(\.[\w\d_-]+)/i, `$1/${name}$2`);

const pkgMain = replaceFilename(pkg.main, pkgname);
const pkgModule = replaceFilename(pkg.module, pkgname);

const input = 'src/index.js';

const files = {
    npm: {
        esm: { file: pkg.module, format: 'esm' },
        umd: { file: pkg.main, format: 'umd', name: clsname },
        esmMin: {
            file: appendMin(pkg.module),
            format: 'esm',
            sourcemap: true,
        },
        umdMin: {
            file: appendMin(pkg.main),
            format: 'umd',
            sourcemap: true,
            name: clsname,
        },
    },
    cdn: {
        esm: { file: pkgModule, format: 'esm' },
        iife: { file: pkgMain, format: 'iife', name: clsname },
        esmMin: {
            file: appendMin(pkgModule),
            format: 'esm',
            sourcemap: true,
        },
        iifeMin: {
            file: appendMin(pkgMain),
            format: 'iife',
            sourcemap: true,
            name: clsname,
        },
    },
};

const terserConfig = {
    format: {
        comments: false,
    },
};

const cdnPlugins = [
    resolve({ browser: true, extensions }),
    commonjs({ include: 'node_modules/**', extensions }),
];

export default [
    {
        // esm && umd bundles for npm/yarn
        input,
        output: [files.npm.esm, files.npm.umd],
        external,
    },
    {
        // esm && umd bundles for npm/yarn (min)
        input,
        output: [files.npm.esmMin, files.npm.umdMin],
        external,
        plugins: [sourceMaps(), terser(terserConfig)],
    },
    {
        // esm bundle for cdn/unpkg
        input,
        output: files.cdn.esm,
        plugins: cdnPlugins,
    },
    {
        // iife bundle for cdn/unpkg
        input,
        output: files.cdn.iife,
        plugins: [...cdnPlugins, babel({ babelHelpers: 'bundled' })],
    },
    {
        // esm bundle from cdn/unpkg (min)
        input,
        output: files.cdn.esmMin,
        plugins: [...cdnPlugins, sourceMaps(), terser(terserConfig)],
    },
    {
        // iife bundle for cdn/unpkg (min)
        input,
        output: files.cdn.iifeMin,
        plugins: [
            ...cdnPlugins,
            sourceMaps(),
            babel({ babelHelpers: 'bundled' }),
            terser(terserConfig),
        ],
    },
];