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The db read-only property of the IDBTransaction interface returns the database connection with which this transaction is associated.

Note: This feature is available in Web Workers.


var myDatabase = transaction.db;


An IDBDatabase object.


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. At the end, we return the associated database connection using db. For a full working example, see our To-do Notifications app (view example live.)

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

DBOpenRequest.onsuccess = function(event) {
  note.innerHTML += '<li>Database initialised.</li>';
  // 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

function addData() {
  // Create a new object ready for being inserted into the IDB
  var 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
  var transaction = db.transaction(["toDoList"], "readwrite");

  // report on the success of opening the transaction
  transaction.oncomplete = function(event) {
    note.innerHTML += '<li>Transaction completed: database modification finished.</li>';

  transaction.onerror = function(event) {
    note.innerHTML += '<li>Transaction not opened due to error. Duplicate items not allowed.</li>';

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

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

  objectStoreRequest.onsuccess = function(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.innerHTML += '<li>Request successful.</li>';

  // Return the database (IDBDatabase) connection with which this transaction is associated


Specification Status Comment
Indexed Database API
The definition of 'db' in that specification.
Indexed Database API 2.0
The definition of 'db' in that specification.

Browser compatibility

FeatureChromeEdgeFirefoxInternet ExplorerOperaSafari
Basic support


23 — 57 webkit



10 — 16 moz

FeatureAndroid webviewChrome for AndroidEdge mobileFirefox for AndroidOpera AndroidiOS SafariSamsung Internet
Basic support


23 — 57 webkit


23 — 57 webkit

Yes22228 ?

1. partial

See also

Document Tags and Contributors

 Contributors to this page: fscholz, chrisdavidmills, jpmedley, libbymc
 Last updated by: fscholz,