rollup.config.js

import svelte from 'rollup-plugin-svelte'
import resolve from '@rollup/plugin-node-resolve'
import browsersync from "rollup-plugin-browsersync"
import { terser } from 'rollup-plugin-terser'
import commonjs from '@rollup/plugin-commonjs'
import pkg from './package.json'
import sveltePreprocess from 'svelte-preprocess'
import postcss from 'rollup-plugin-postcss'

const watch = process.env.WATCH
const mainpath = watch ? 'docs/index.js': pkg.main
const dedupe = [ 'svelte' ]

const scssOptions = {
  transformers: {
    scss: {
      includePaths: [
        'node_modules',
        'src'
      ]
    },
    postcss: {
      plugins: [
        require('autoprefixer')
      ]
    }
  }
}

export default {
	input: 'src/index.js',
	output: [
		{ file: pkg.module, format: 'es' },
		{ file: mainpath, format: 'iife' }
	],
	plugins: [
		commonjs(),
		svelte({
			preprocess: sveltePreprocess(scssOptions)
		}),
		resolve({
			dedupe
		}),
		postcss(),
		watch && browsersync({ server: 'docs' }),
		!watch && terser()
	]
}