(async () => {
  let file;
  {
    const db = await open();
    const trans = db.transaction("foo", "readwrite");
    const store = trans.objectStore("foo");
    store.put(new Blob(["bar"]), "foo");
    await complete(trans);
    db.close();
  }
  {
    const db = await open();
    const trans = db.transaction("foo", "readonly");
    const store = trans.objectStore("foo");
    file = await success(store.get("foo"));
    await complete(trans);
    db.close();
  }
  {
    const db = await open();
    const trans = db.transaction("foo", "readwrite");
    const store = trans.objectStore("foo");
    store.delete("foo");
    await complete(trans);
    db.close();
  }
  try {
    console.log(await fetch(URL.createObjectURL(file)));
  } catch (err) {
    console.log("fetch err", err);
  }
  try {
    console.log(await blobToBuffer(file));
  } catch (err) {
    console.log("file reader err", err);
  }
  
  function blobToBuffer(blob) {
    return new Promise((resolve, reject) => {
      const reader = new FileReader;
      reader.onload = () => resolve(reader.result);
      reader.onerror = reject;
      reader.readAsArrayBuffer(blob);
    });
  }
  
  function open() {
    return new Promise((resolve, reject) => {
      const request = indexedDB.open("ff-idb-blob-test", 1);
      request.onupgradeneeded = e => {
        e.target.result.createObjectStore("foo");
      };
      request.onsuccess = e => {
        resolve(request.result);
      };
      request.onerror = reject;
    });
  }

  function success(r) {
    return new Promise((resolve, reject) => {
      r.onsuccess = () => resolve(r.result);
      r.onerror = reject;
    });
  }
  
  function complete(r) {
    return new Promise((resolve, reject) => {
      r.oncomplete = resolve;
      r.onerror = reject;
    });
  }
})();