rollup.config.js

const tsc = require('@rollup/plugin-typescript');
const cleanup = require('rollup-plugin-cleanup');
const copy = require('rollup-plugin-copy');
const nodeResolve = require('@rollup/plugin-node-resolve').default;
const injectCode = require('./plugins/rollup-plugin-inject-code');

const extensions = ['.ts', '.js'];

module.exports = {
  input: 'src/index.ts',
  output: {
    file: 'dist/adoptedStyleSheets.js',
    format: 'iife',
    name: 'adoptedStyleSheets',
  },
  plugins: [
    nodeResolve({
      extensions,
    }),
    tsc({
      isolatedModules: true,
      tsconfig: require.resolve('./tsconfig.build.json'),
    }),
    cleanup({
      extensions,
    }),
    copy({
      targets: [
        {
          src: 'src/typings.d.ts',
          dest: 'dist',
          rename: 'adoptedStyleSheets.d.ts',
        },
      ],
    }),
    injectCode({
      'adoptedStyleSheets.js': {
        line: 3,
        code:
          "    if (typeof document === 'undefined' || 'adoptedStyleSheets' in document) { return; }\n",
      },
    }),
  ],
};