IDBRequest: transaction 属性

const title = "Walk dog";

// Open up a transaction as usual
const objectStore = db
  .transaction(["toDoList"], "readwrite")
  .objectStore("toDoList");

// Get the to-do list object that has this title as its title
const objectStoreTitleRequest = objectStore.get(title);

objectStoreTitleRequest.onsuccess = () => {
  // Grab the data object returned as the result
  const data = objectStoreTitleRequest.result;

  // Update the notified value in the object to "yes"
  data.notified = "yes";

  // Create another request that inserts the item back
  // into the database
  const updateTitleRequest = objectStore.put(data);

  // Log the transaction that originated this request
  console.log(
    `The transaction that originated this request is ${updateTitleRequest.transaction}`,
  );

  // When this new request succeeds, run the displayData()
  // function again to update the display
  updateTitleRequest.onsuccess = () => {
    displayData();
  };
};

const openRequest = indexedDB.open("db", 2);
console.log(openRequest.transaction); // Will log "null".

openRequest.onupgradeneeded = (event) => {
  console.log(openRequest.transaction.mode); // Will log "versionchange".
  const db = openRequest.result;
  if (event.oldVersion < 1) {
    // New database, create "books" object store.
    db.createObjectStore("books");
  }
  if (event.oldVersion < 2) {
    // Upgrading from v1 database: add index on "title" to "books" store.
    const bookStore = openRequest.transaction.objectStore("books");
    bookStore.createIndex("by_title", "title");
  }
};

openRequest.onsuccess = () => {
  console.log(openRequest.transaction); // Will log "null".
};