rollup.config.ts

import resolve from 'rollup-plugin-node-resolve'
import sourceMaps from 'rollup-plugin-sourcemaps'
import typescript from 'rollup-plugin-typescript2'

const pkg = require('./package.json')

const entryFile = 'index'
const banner = `
/*!
 * ${pkg.name} v${pkg.version} by ${pkg.author}
 * ${pkg.homepage || `https://github.com/${pkg.repository}`}
 * @license ${pkg.license}
 */
`.trim()

const defaultExportOutro = `
  module.exports = exports.default || {}
  Object.entries(exports).forEach(([key, value]) => { module.exports[key] = value })
`

export default {
  input: `src/${entryFile}.ts`,
  output: [
    {
      file: pkg.main,
      format: 'cjs',
      sourcemap: true,
      exports: 'named',
      outro: defaultExportOutro,
      banner
    },
    {
      file: pkg.module,
      format: 'es',
      sourcemap: true,
      exports: 'named',
      banner
    }
  ],
  // Indicate here external modules you don't wanna include in your bundle (i.e.: 'lodash')
  external: [
    ...Object.keys(pkg.dependencies || {}),
    ...Object.keys(pkg.peerDependencies || {})
  ],
  watch: {
    include: 'src/**'
  },
  plugins: [
    // Compile TypeScript files
    typescript({ useTsconfigDeclarationDir: true }),
    // Allow bundling cjs modules (unlike webpack, rollup doesn't understand cjs)
    // commonjs(),
    // Allow node_modules resolution, so you can use 'external' to control
    // which external modules to include in the bundle
    // https://github.com/rollup/rollup-plugin-node-resolve#usage
    resolve(),
    // Resolve source maps to the original source
    sourceMaps()
  ]
}