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.
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.
This method may raise a DOMException of one of the following types:
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TransactionInactiveError DOMException
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Thrown if this IDBCursor's transaction is inactive.
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ReadOnlyError DOMException
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Thrown if the transaction mode is read-only.
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InvalidStateError DOMException
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Thrown if the cursor was created using IDBindex.openKeyCursor, is currently being iterated, or has iterated past its end.
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DataError DOMException
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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.
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DataCloneError DOMException
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Thrown if the data being stored could not be cloned by the internal structured cloning algorithm.
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).
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.");
}
};
}