Bootstrap/build/rollup.config.js

'use strict'

const path = require('path')
const { babel } = require('@rollup/plugin-babel')
const { nodeResolve } = require('@rollup/plugin-node-resolve')
const banner = require('./banner.js')

const BUNDLE = process.env.BUNDLE === 'true'

let fileDest = 'bootstrap.js'
const external = ['jquery', 'popper.js']
const plugins = [
  babel({
    // Only transpile our source code
    exclude: 'node_modules/**',
    // Include the helpers in the bundle, at most one copy of each
    babelHelpers: 'bundled'
  })
]
const globals = {
  jquery: 'jQuery', // Ensure we use jQuery which is always available even in noConflict mode
  'popper.js': 'Popper'
}

if (BUNDLE) {
  fileDest = 'bootstrap.bundle.js'
  // Remove last entry in external array to bundle Popper
  external.pop()
  delete globals['popper.js']
  plugins.push(nodeResolve())
}

module.exports = {
  input: path.resolve(__dirname, '../js/index.js'),
  output: {
    banner,
    file: path.resolve(__dirname, `../dist/js/${fileDest}`),
    format: 'umd',
    globals,
    name: 'bootstrap'
  },
  external,
  plugins
}