The openKeyCursor()
method of the IDBIndex
interface returns an IDBRequest
object, and, in a separate thread, creates a cursor over the specified key range, as arranged by this index.
The method sets the position of the cursor to the appropriate key, based on the specified direction.
- If the key range is not specified or is null, then the range includes all the keys.
- A success event is always fired on the result object.
- If at least one key matches the key range, then the
result
property of the event is set to the newIDBCursor
object; thekey
property of the cursor object is set to the found key and theprimaryKey
property is set to the the corresponding primary key of the found record. - If no keys match the key range, then then the
result
property of the event is set tonull
.
- If at least one key matches the key range, then the
Note: Cursors returned by openKeyCursor()
do not make the referenced value available as IDBIndex.openCursor
does. This makes obtaining a list of keys much more efficient.
Syntax
var request = myIndex.openKeyCursor(); var request = myIndex.openKeyCursor(range); var request = myIndex.openKeyCursor(range, direction);
Parameters
- range Optional
- A key or
IDBKeyRange
to use as the cursor's range. If nothing is passed, this will default to a key range that selects all the records in this object store. - direction Optional
- The cursor's direction. See IDBCursor Constants for possible values.
Return value
An IDBRequest
object on which subsequent events related to this operation are fired.
Exceptions
This method may raise a DOMException
of one of the following types:
Exception | Description |
---|---|
TransactionInactiveError |
This IDBIndex 's transaction is inactive. |
TypeError |
The value for the direction parameter is invalid. |
DataError |
The key or key range provided contains an invalid key. |
InvalidStateError |
The IDBIndex has been deleted or removed. |
Example
In the following example we open a transaction and an object store, then get the index lName
from a simple contacts database. We then open a key cursor on the index using openKeyCursor()
— this works the same as opening a cursor directly on an ObjectStore
using IDBObjectStore.openKeyCursor
except that the returned records are sorted based on the index, not the primary key.
Finally, we iterate through each record in the index, and insert the last name and the corresponding primary key of the referenced record into an HTML table.
function displayDataByIndex() { tableEntry.innerHTML = ''; var transaction = db.transaction(['contactsList'], 'readonly'); var objectStore = transaction.objectStore('contactsList'); var myIndex = objectStore.index('lName'); myIndex.openKeyCursor().onsuccess = function(event) { var cursor = event.target.result; if(cursor) { var tableRow = document.createElement('tr'); tableRow.innerHTML = '<td>' + cursor.key + '</td>' + '<td>' + cursor.primaryKey + '</td>'; tableEntry.appendChild(tableRow); cursor.continue(); } else { console.log('All last names displayed.'); } }; };
Specification
Specification | Status | Comment |
---|---|---|
Indexed Database API 2.0 The definition of 'openKeyCursor()' in that specification. |
Recommendation | |
Indexed Database API Draft The definition of 'openKeyCursor()' in that specification. |
Recommendation |
Browser compatibility
Desktop | Mobile | |||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|
openKeyCursor | Chrome
Full support
24
| Edge Full support 12 | Firefox
Full support
16
| IE Partial support 10 | Opera Full support 15 | Safari Full support 7 | WebView Android
Full support
Yes
| Chrome Android Full support 25 | Firefox Android Full support 22 | Opera Android Full support 14 | Safari iOS Full support 8 | Samsung Internet Android Full support 1.5 |
Legend
- Full support
- Full support
- Partial support
- Partial support
- Requires a vendor prefix or different name for use.
- Requires a vendor prefix or different name for use.
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 example live.)