IDBObjectStore: openCursor() method
The openCursor()
method of the
IDBObjectStore
interface returns an IDBRequest
object,
and, in a separate thread, returns a new IDBCursorWithValue
object.
Used for iterating through an object store with a cursor.
To determine if the add operation has completed successfully, listen for the results's
success
event.
Note: This feature is available in Web Workers
Syntax
js
openCursor()
openCursor(query)
openCursor(query, direction)
Parameters
query
Optional-
A key or
IDBKeyRange
to be queried. If a single valid key is passed, this will default to a range containing only that key. If nothing is passed, this will default to a key range that selects all the records in this object store. direction
Optional-
A string telling the cursor which direction to travel. The default is
next
. Valid values are:next
-
The cursor is opened at the start of the store; then, the cursor returns all records, even duplicates, in the increasing order of keys.
nextunique
-
The cursor is opened at the start of the store; then, the cursor returns all records, that are not duplicates, in the increasing order of keys.
prev
-
The cursor is opened at the start of the store; then, the cursor returns all records, even duplicates, in the decreasing order of keys.
prevunique
-
The cursor is opened at the start of the store; then, the cursor returns all records, that are not duplicates, in the decreasing order of keys.
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:
- an
IDBCursorWithValue
object pointing at the first record matching the given query null
if no matching records were found.
Exceptions
This method may raise a DOMException
of one of the following types:
InvalidStateError
DOMException
-
Thrown if this
IDBObjectStore
orIDBIndex
has been deleted. TransactionInactiveError
DOMException
-
Thrown if this
IDBObjectStore
's transaction is inactive. DataError
DOMException
-
Thrown if the specified key or key range is invalid.
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:
js
const transaction = db.transaction("name", "readonly");
const objectStore = transaction.objectStore("name");
const request = objectStore.openCursor();
request.onsuccess = (event) => {
const cursor = event.target.result;
if (cursor) {
// cursor.value contains the current record being iterated through
// this is where you'd do something with the result
cursor.continue();
} else {
// no more results
}
};
Specifications
Specification |
---|
Indexed Database API 3.0 # ref-for-dom-idbobjectstore-opencursor② |
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).