@date-io/core/dev-utils.js

const nodeResolve = require("rollup-plugin-node-resolve");
const typescriptPlugin = require("rollup-plugin-typescript");

exports.createRollupConfig = (typescript) => {
  const extensions = [".ts", ".tsx"];

  // treat as externals not relative and not absolute paths
  const external = (id) => !id.startsWith(".") && !id.startsWith("/");

  return [
    {
      external,
      input: `src/index.ts`,
      output: {
        file: `build/index.esm.js`,
        format: "esm",
        exports: "auto",
      },
      plugins: [
        nodeResolve({ extensions }),
        typescriptPlugin({ typescript, target: "ES6" }),
      ],
    },
    {
      external,
      input: `src/index.ts`,
      output: {
        file: `build/index.js`,
        format: "cjs",
        exports: "auto",
      },
      plugins: [
        nodeResolve({ extensions }),
        typescriptPlugin({ typescript, target: "ES6" }),
      ],
    },
  ];
};