rollup.config.js

import {flatMap, compact} from 'lodash'
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 license from 'rollup-plugin-license'

import pkg from './package.json'

const banner = `
<%= pkg.name %> <%= pkg.version %>
MIT Licensed 
Generated by <%= pkg.authors[0] %>
Generated at <%= moment().format('YYYY-MM-DD') %>
`
export default flatMap(['none', 'shouldMinify', 'noClassesTranspile', 'both'], buildMode => {
  const shouldMinify = buildMode === 'shouldMinify' || buildMode === 'both'
  const shouldTranspileClasses = buildMode === 'none' || buildMode === 'both'

  const babelPlugins = compact([
    shouldTranspileClasses && '@babel/plugin-transform-classes'
  ])

  return [
    {
      input: 'src/index.js',
      output: {
        name: 'whyDidYouRender',
        file: (shouldTranspileClasses ? pkg.browser : pkg['browser-no-classes-transpile'])
          .replace('.min', shouldMinify ? '.min' : ''),
        format: 'umd',
        sourcemap: shouldMinify,
        sourcemapFile: pkg.browser.replace('.js', '.js.map')
      },
      plugins: [
        babel({
          exclude: 'node_modules/**',
          plugins: babelPlugins
        }),
        resolve(),
        commonjs(),
        shouldMinify && terser(),
        license({
          sourcemap: true,
          banner
        })
      ]
    },
    {
      input: 'src/index.js',
      output: [
        {
          file: (shouldTranspileClasses ? pkg.main : pkg['main-no-classes-transpile'])
            .replace('.min', shouldMinify ? '.min' : ''),
          format: 'cjs',
          sourcemap: shouldMinify,
          sourcemapFile: pkg.main.replace('.js', '.js.map')
        },
        {
          file: (shouldTranspileClasses ? pkg.module : pkg['module-no-classes-transpile'])
            .replace('.min', shouldMinify ? '.min' : ''),
          format: 'esm',
          sourcemap: shouldMinify,
          sourcemapFile: pkg.module.replace('.js', '.js.map')
        }
      ],
      plugins: [
        babel({
          exclude: 'node_modules/**',
          plugins: babelPlugins
        }),
        resolve(),
        commonjs(),
        shouldMinify && terser(),
        license({
          sourcemap: true,
          banner
        })
      ],
      external: id => /lodash/.test(id)
    }
  ]
})