rollup.config.js

const UglifyJS = require('uglify-es')
const resolve = require('rollup-plugin-node-resolve')
const commonjs = require('rollup-plugin-commonjs')
const uglify = require('rollup-plugin-uglify').uglify
const json = require('rollup-plugin-json')
const replace = require('rollup-plugin-replace')
const filesize = require('rollup-plugin-filesize')
const buble = require('rollup-plugin-buble')

let production = function () {
  return !process.env.ROLLUP_WATCH
}

module.exports = {
  input: 'src/measurement-framework.js',
  output: {
    name: 'measurementFramework',
    file: 'dist/measurement-framework.js',
    format: 'iife', // immediately-invoked function expression — suitable for <script> tags
    globals: {
      window: 'window',
      document: 'document'
    }
  },
  treeshake: true,
  external: ['window', 'document'],
  plugins: [
    json(),
    replace({
      'RMFBUILDTIME': new Date().toISOString()
    }),
    resolve({
      mainFields: [
        ['jsnext', 'jsnext:main', true]
      ],
      browser: true, // Default: false
      extensions: ['.js', '.json'], // Default: ['.js']
      preferBuiltins: true, // Default: true
      modulesOnly: false, // Default: false
      customResolveOptions: {}
    }), // tells Rollup how to find date-fns in node_modules
    commonjs(), // converts date-fns to ES modules
    buble(),
    production() && uglify({
      toplevel: true,
      ie8: true,
      mangle: true,
      compress: {
        toplevel: true,
        drop_console: true
        // reduce_vars: false
      }
    }, UglifyJS.minify), // minify, but only in production
    filesize()
  ]
}