rollup/rollup-plugin-commonjs

npm install --save-dev rollup-plugin-commonjs

// rollup.config.js
import commonjs from 'rollup-plugin-commonjs';
import nodeResolve from 'rollup-plugin-node-resolve';

export default {
  input: 'main.js',
  output: {
    file: 'bundle.js',
    format: 'iife'
  },
  plugins: [
    nodeResolve({
      jsnext: true,
      main: true
    }),

    commonjs({
      // non-CommonJS modules will be ignored, but you can also
      // specifically include/exclude files
      include: 'node_modules/**',  // Default: undefined
      exclude: [ 'node_modules/foo/**', 'node_modules/bar/**' ],  // Default: undefined
      // these values can also be regular expressions
      // include: /node_modules/

      // search for files other than .js files (must already
      // be transpiled by a previous plugin!)
      extensions: [ '.js', '.coffee' ],  // Default: [ '.js' ]

      // if true then uses of `global` won't be dealt with by this plugin
      ignoreGlobal: false,  // Default: false

      // if false then skip sourceMap generation for CommonJS modules
      sourceMap: false,  // Default: true

      // explicitly specify unresolvable named exports
      // (see below for more details)
      namedExports: { 'react': ['createElement', 'Component' ] },  // Default: undefined

      // sometimes you have to leave require statements
      // unconverted. Pass an array containing the IDs
      // or a `id => boolean` function. Only use this
      // option if you know what you're doing!
      ignore: [ 'conditional-runtime-dependency' ]
    })
  ]
};

commonjs({
  include: /node_modules/
})

// importer.js
import { named } from './exporter.js';

// exporter.js
module.exports = { named: 42 }; // or `exports.named = 42;`

// importer.js
import { named } from 'my-lib';

// my-lib.js
var myLib = exports;
myLib.named = 'you can\'t see me';

commonjs({
  namedExports: {
    // left-hand side can be an absolute path, a path
    // relative to the current directory, or the name
    // of a module in node_modules
    'my-lib': [ 'named' ]
  }
})