index.js

(async () => {
  const inPath = "./example.mdx";
  const outPath = "./example-out.mdx";

  const file = await read(inPath);
  const processor = remark().use(mdx);
  const tree = processor.parse(file.contents.toString());
  const result = processor.stringify(tree);
  console.log("result", result);
  await write({
    path: outPath,
    result
  });
})();