native-fs-read-example.ts

import "regenerator-runtime/runtime";
const tx = document.createElement("textarea") as HTMLTextAreaElement;
document.body.appendChild(tx);

const btn = document.createElement("button");
btn.textContent = "start";
document.body.appendChild(btn);
btn.addEventListener("click", async (ev: any) => {
  // @ts-ignore
  const fileHandler = await window.chooseFileSystemEntries();
  const file = await fileHandler.getFile();
  tx.value = await file.text();
});