const tx = db.transaction("books", "readonly");
const store = tx.objectStore("books");
const index = store.index("by_title");

const request = index.get("Bedrock Nights");
request.onsuccess = function() {
  const matching = request.result;
  if (matching !== undefined) {
    // A match was found.
    report(matching.isbn, matching.title, matching.author);
  } else {
    // No match was found.
    report(null);
  }
};