The mode
read-only property of the IDBTransaction
interface returns the current mode for accessing the data in the object stores in the scope of the transaction (i.e. is the mode to be read-only, or do you want to write to the object stores?) The default value is readonly
.
An object defining the mode for isolating access to data 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 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 IDBDatabase.setVersion()
. Transactions of this mode cannot run concurrently with other transactions. Transactions in this mode are known as upgrade transactions.
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 log the mode of the current transaction using mode
. For a full working example, see our To-do Notifications app (view example live).
const note = document.getElementById("notifications");
let db;
const DBOpenRequest = window.indexedDB.open("toDoList", 4);
DBOpenRequest.onsuccess = (event) => {
note.innerHTML += "<li>Database initialized.</li>";
db = DBOpenRequest.result;
addData();
};
function addData() {
const newItem = [
{
taskTitle: "Walk dog",
hours: 19,
minutes: 30,
day: 24,
month: "December",
year: 2013,
notified: "no",
},
];
const transaction = db.transaction(["toDoList"], "readwrite");
transaction.oncomplete = (event) => {
note.innerHTML +=
"<li>Transaction completed: database modification finished.</li>";
};
transaction.onerror = (event) => {
note.innerHTML +=
"<li>Transaction not opened due to error. Duplicate items not allowed.</li>";
};
const objectStore = transaction.objectStore("toDoList");
const objectStoreRequest = objectStore.add(newItem[0]);
objectStoreRequest.onsuccess = (event) => {
note.innerHTML += "<li>Request successful.</li>";
};
transaction.mode;
}