IDBTransaction: mode property

BaselineWidely available

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

Note: This feature is available inWeb Workers.

Themode read-only property of theIDBTransaction interface returns the current mode for accessing thedata in the object stores in the scope of the transaction (i.e., is the mode to beread-only, or do you want to write to the object stores?) The default value isreadonly.

Value

An object defining the mode for isolating access todata in the current object stores:A string defining the mode for isolating access to data in the current object stores.The following values are available:

readonly: Allows data to be read but not changed.
readwrite: Allows reading and writing of data in existing data stores to be changed.
versionchange: Allows any operation, including ones that delete andcreate object stores and indexes.This mode is for updating the version number of transactions if the need is detected when callingIDBFactory.open().Transactions of this mode cannot run concurrently with other transactions.Transactions in this mode are known asupgrade transactions.

Examples

In the following code snippet, we open a read/write transaction on our database and addsome data to an object store. Note also the functions attached to transaction eventhandlers to report on the outcome of the transaction opening in the event of success orfailure. At the end, we log the mode of the current transaction usingmode.For a full working example, see ourTo-do Notifications app (view example live).

const note = document.getElementById("notifications");// an instance of a db object for us to store the IDB data inlet db;// Let us open our databaseconst 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. Duplicate items not allowed.";  };  // 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.";  };  // Return the mode this transaction has been opened in (should be "readwrite" in this case)  transaction.mode;}