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    IDBTransaction

    This article is in need of a technical review.

    The IDBTransaction interface of the IndexedDB API provides a static, asynchronous transaction on a database using event handler attributes. All reading and writing of data is done within transactions. You actually use IDBDatabase to start transactions and IDBTransaction to set the mode of the transaction (e.g. is it readonly or readwrite), and access an IDBObjectStore to make a request. You can also use it to abort transactions.

    Note that as of Firefox 40, IndexedDB transactions have relaxed durability guarantees to increase performance (see bug 1112702.) Previously in a readwrite transaction IDBTransaction.oncomplete was fired only when all data was guaranteed to have been flushed to disk. In Firefox 40+ the complete event is fired after the OS has been told to write the data but potentially before that data has actually been flushed to disk. The complete event may thus be delivered quicker than before, however, there exists a small chance that the entire transaction will be lost if the OS crashes or there is a loss of system power before the data is flushed to disk. Since such catastrophic events are rare most consumers should not need to concern themselves further.

    If you must ensure durability for some reason (e.g. you're storing critical data that cannot be recomputed later) you can force a transaction to flush to disk before delivering the complete event by creating a transaction using the experimental (non-standard) readwriteflush mode (see IDBDatabase.transaction.

    Methods

    Inherits from: EventTarget

    IDBTransaction.abort
    Rolls back all the changes to objects in the database associated with this transaction. If this transaction has been aborted or completed, then this method throws an error event.
    IDBTransaction.objectStore
    Returns an IDBObjectStore object representing an object store that is part of the scope of this transaction.

    Properties

    IDBTransaction.db Read only
    The database connection with which this transaction is associated.
    IDBTransaction.mode Read only
    The mode for isolating access to data in the object stores that are in the scope of the transaction. For possible values, see the Constants section below. The default value is readonly.
    IDBTransaction.error Read only
    The error returned in the event of an unsuccessful transaction. Null if the transaction is not finished, is finished and successfully committed, or was aborted with IDBTransaction.abort function. Returns the same DOMError as the request object which caused the transaction to be aborted due to a failed request, or a DOMError for the transaction failure not due to a failed request (such as QuotaExceededError or UnknownError).

    Event handlers

    IDBTransaction.onabort Read only
    The event handler for the abort event, fired when the transaction is aborted.
    IDBTransaction.oncomplete Read only
    The event handler for the complete event, thrown when the transaction completes successfully.
    IDBTransaction.onerror Read only
    The event handler for the error event, thrown when the transaction fails to complete.

    Mode constants

    Obsolete since Gecko 25 (Firefox 25 / Thunderbird 25 / SeaMonkey 2.22)
    This feature is obsolete. Although it may still work in some browsers, its use is discouraged since it could be removed at any time. Try to avoid using it.

    These constants are no longer available. You should use the direct string constants instead. (bug 888598)

    Transactions can have one of three modes:

    Constant Value Description
    READ_ONLY

    "readonly"

    (0 in Chrome)

    Allows data to be read but not changed.

    READ_WRITE

    "readwrite"

    (1 in Chrome)

    Allows reading and writing of data in existing data stores to be changed.
    VERSION_CHANGE

    "versionchange"

    (2 in Chrome)

    Allows any operation to be performed, including ones that delete and create object stores and indexes. This mode is for updating the version number of transactions that were started using the setVersion() method of IDBDatabase objects. Transactions of this mode cannot run concurrently with other transactions.

    Even if these constants are now deprecated, you can still use them to provide backward compatibility if required (in Chrome the change was made in version 21). You should code defensively in case the object is not available anymore:

    var myIDBTransaction = window.IDBTransaction || window.webkitIDBTransaction || { READ_WRITE: "readwrite" };

    Example

    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. 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
      addData();
    };
    
    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 our new item going into the database
        note.innerHTML += '<li>New item added to database.</li>';
      };
    };

    Specifications

    Specification Status Comment
    Indexed Database API
    The definition of 'IDBTransaction' in that specification.
    Candidate Recommendation  

    Browser compatibility

    Feature Chrome Firefox (Gecko) Internet Explorer Opera Safari (WebKit)
    Basic support 23webkit
    24
    10 moz
    16.0 (16.0)
    10, partial 15 7.1
    Feature Android Firefox Mobile (Gecko) Firefox OS IE Phone Opera Mobile Safari Mobile
    Basic support 4.4 22.0 (22.0) 1.0.1 10 22 Not supported

    Known browser issues

    Older versions of Google Chrome serialise all transactions. So even if you have only read-only transactions and no read-write transaction, your transactions are executed one at a time. Any subsequent transactions are not executed until read-only transactions are completed. For the status, see bug 64076.

    See also

    Document Tags and Contributors

    Last updated by: chrisdavidmills,