IDBTransaction: error property

Baseline Widely available *

This feature is well established and works across many devices and browser versions. It’s been available across browsers since July 2015.

* Some parts of this feature may have varying levels of support.

Note: This feature is available in Web Workers.

The IDBTransaction.error property of the IDBTransaction interface returns the type of error when there is an unsuccessful transaction.

Value

A DOMException containing the relevant error, or null if there are none.

It can be a reference to the same error as the request object that raised it, or a transaction failure (for example QuotaExceededError).

This property is null if the transaction is not finished, or is finished and was successfully committed.

In the following code snippet, we open a read/write transaction on our database and add some data to an object store. Note also the functions attached to transaction event handlers to report on the outcome of the transaction opening in the event of success or failure. Note the transaction.onerror = (event) => { }; block, making use of transaction.error to help in reporting what went wrong when the transaction was unsuccessful. For a full working example, see our To-do Notifications app (View example live).

js
const note = document.getElementById("notifications");

// an instance of a db object for us to store the IDB data in
let db;

// Let us open our database
const DBOpenRequest = window.indexedDB.open("toDoList", 4);

DBOpenRequest.onsuccess = (event) => {
  note.appendChild(document.createElement("li")).textContent =
    "Database initialized.";

  // store the result of opening the database in the db variable.
  // This is used a lot below
  db = DBOpenRequest.result;

  // Run the addData() function to add the data to the database
  addData();
};

function addData() {
  // Create a new object ready for being inserted into the IDB
  const newItem = [
    {
      taskTitle: "Walk dog",
      hours: 19,
      minutes: 30,
      day: 24,
      month: "December",
      year: 2013,
      notified: "no",
    },
  ];

  // open a read/write db transaction, ready for adding the data
  const transaction = db.transaction(["toDoList"], "readwrite");

  // report on the success of opening the transaction
  transaction.oncomplete = (event) => {
    note.appendChild(document.createElement("li")).textContent =
      "Transaction completed: database modification finished.";
  };

  transaction.onerror = (event) => {
    note.appendChild(document.createElement("li")).textContent =
      `Transaction not opened due to error: ${transaction.error}`;
  };

  // create an object store on the transaction
  const objectStore = transaction.objectStore("toDoList");

  // add our newItem object to the object store
  const objectStoreRequest = objectStore.add(newItem[0]);

  objectStoreRequest.onsuccess = (event) => {
    // report the success of the request (this does not mean the item
    // has been stored successfully in the DB - for that you need transaction.onsuccess)
    note.appendChild(document.createElement("li")).textContent =
      "Request successful.";
  };
}