IDBCursor: update() method
The update()
method of the IDBCursor
interface returns an IDBRequest
object, and, in a separate thread,
updates the value at the current position of the cursor in the object store. If the
cursor points to a record that has just been deleted, a new record is created.
Be aware that you can't call update()
(or
IDBCursor.delete()
) on cursors obtained from
IDBIndex.openKeyCursor()
. For such needs, you have to use
IDBIndex.openCursor()
instead.
Note: This feature is available in Web Workers
Syntax
js
update(value)
Parameters
value
-
The new value to be stored at the current position.
Return value
An IDBRequest
object on which subsequent events related to this operation are fired.
If the operation is successful, the value of the request's result
property is the key for the updated record.
Exceptions
This method may raise a DOMException
of one of the following types:
TransactionInactiveError
DOMException
-
Thrown if this IDBCursor's transaction is inactive.
ReadOnlyError
DOMException
-
Thrown if the transaction mode is read-only.
InvalidStateError
DOMException
-
Thrown if the cursor was created using
IDBindex.openKeyCursor
, is currently being iterated, or has iterated past its end. DataError
DOMException
-
Thrown if the underlying object store uses in-line keys and the property in the value at the object store's key path does not match the key in this cursor's position.
DataCloneError
DOMException
-
Thrown if the data being stored could not be cloned by the internal structured cloning algorithm.
Examples
In this simple fragment we create a transaction, retrieve an object store, then use a
cursor to iterate through all the records in the object store. If the
albumTitle
of the current cursor is "A farewell to kings", we update year
the album was released using const request = cursor.update();
.
Note that you cannot change primary keys using cursor.update()
, hence us
not changing the album title; this would ruin the integrity of the data. In such a
situation, you would have to delete the record altogether and then add a new one using
IDBObjectStore.add
. Note also that you can't directly put
cursor.value
into an update call, hence the below example using an
intermediary updateData
variable.
The cursor does not require us to select the data based
on a key; we can just grab all of it. Also note that in each iteration of the loop,
you can grab data from the current record under the cursor object using cursor.value.foo
. For a complete working example, see our IDBCursor example (View the example live).
js
function updateResult() {
list.textContent = "";
const transaction = db.transaction(["rushAlbumList"], "readwrite");
const objectStore = transaction.objectStore("rushAlbumList");
objectStore.openCursor().onsuccess = (event) => {
const cursor = event.target.result;
if (cursor) {
if (cursor.value.albumTitle === "A farewell to kings") {
const updateData = cursor.value;
updateData.year = 2050;
const request = cursor.update(updateData);
request.onsuccess = () => {
console.log("A better album year?");
};
}
const listItem = document.createElement("li");
listItem.textContent = `${cursor.value.albumTitle}, ${cursor.value.year}`;
list.appendChild(listItem);
cursor.continue();
} else {
console.log("Entries displayed.");
}
};
}
Specifications
Specification |
---|
Indexed Database API 3.0 # ref-for-dom-idbcursor-update① |
Browser compatibility
BCD tables only load in the browser
See also
- Using IndexedDB
- Starting transactions:
IDBDatabase
- Using transactions:
IDBTransaction
- Setting a range of keys:
IDBKeyRange
- Retrieving and making changes to your data:
IDBObjectStore
- Using cursors:
IDBCursor
- Reference example: To-do Notifications (View the example live).