rollup.config.js

import commonjs from '@rollup/plugin-commonjs';
import nodeResolve from '@rollup/plugin-node-resolve';
import path from 'path';
import typescript2 from 'rollup-plugin-typescript2';
import packageJson from './package.json';

const COMMONJS_EXTENSION = 'cjs';
const ESM_EXTENSION = 'js';
const IS_DEV = process.env.NODE_ENV === 'development';
const MAIN_DIR = path.parse(packageJson.main).dir;
const MODULE_DIR = path.parse(packageJson.module).dir;
const TSCONFIG = IS_DEV ? './tsconfig.development.json' : './tsconfig.json';

const EXTERNAL = new Set(Object.keys(packageJson.peerDependencies));

export default [
  {
    cache: true,
    input: 'src/index.ts',
    treeshake: !IS_DEV,
    external(id) {
      if (EXTERNAL.has(id)) {
        return true;
      }

      for (const pkg of EXTERNAL) {
        if (id.startsWith(`${pkg}/`)) {
          return true;
        }
      }

      return false;
    },
    output: [
      {
        chunkFileNames: `[name]-[hash].${COMMONJS_EXTENSION}`,
        dir: MAIN_DIR,
        entryFileNames: `[name].${COMMONJS_EXTENSION}`,
        exports: 'named',
        format: 'cjs',
        sourcemap: IS_DEV,
      },
      {
        chunkFileNames: `[name]-[hash].${ESM_EXTENSION}`,
        dir: MODULE_DIR,
        entryFileNames: `[name].${ESM_EXTENSION}`,
        format: 'es',
        sourcemap: IS_DEV,
      },
    ],
    plugins: [
      nodeResolve({
        extensions: ['.js', '.jsx', '.ts', '.tsx'],
        preferBuiltins: true,
      }),
      commonjs({
        extensions: ['.js', '.jsx'],
      }),
      typescript2({
        check: !IS_DEV,
        tsconfig: TSCONFIG,
        useTsconfigDeclarationDir: true,
      }),
    ],
    watch: {
      exclude: 'node_modules/**',
    },
  },
];