IDBIndex.getKey()
The getKey()
method of the IDBIndex
interface returns an IDBRequest
object, and, in a separate thread,
finds either the primary key that corresponds to the given key in this index or the
first corresponding primary key, if key
is set to an
IDBKeyRange
.
If a primary key is found, it is set as the result
of the request object.
Note that this doesn't return the whole record as IDBIndex.get
does.
Note: This feature is available in Web Workers
Syntax
var request = myIndex.getKey(key);
Parameters
- key Optional
-
A key or
IDBKeyRange
that identifies a record to be retrieved. If this value is null or missing, the browser will use an unbound key range.
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:
TransactionInactiveError
DOMException
-
Thrown if this
IDBIndex
's transaction is inactive. DataError
DOMException
-
Thrown if the key or key range provided contains an invalid key.
InvalidStateError
DOMException
-
Thrown if 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 basic cursor on
the index using IDBIndex.openCursor
— this works the same as opening a
cursor directly on an ObjectStore
using
IDBObjectStore.openCursor
except that the returned records are sorted
based on the index, not the primary key.
myIndex.getKey('Bungle')
is then used to retrieve the primary key of the
record with an lName
of Bungle
, and the result of that request
is logged to the console when its success callback returns.
Finally, we iterate through each record, and insert the data into an HTML table. For a complete working example, see our IndexedDB-examples demo repo (View the example live.)
function displayDataByIndex() {
tableEntry.innerHTML = '';
var transaction = db.transaction(['contactsList'], 'readonly');
var objectStore = transaction.objectStore('contactsList');
var myIndex = objectStore.index('lName');
var getKeyRequest = myIndex.getKey('Bungle');
getKeyRequest.onsuccess = function() {
console.log(getKeyRequest.result);
}
myIndex.openCursor().onsuccess = function(event) {
var cursor = event.target.result;
if(cursor) {
var tableRow = document.createElement('tr');
tableRow.innerHTML = '<td>' + cursor.value.id + '</td>'
+ '<td>' + cursor.value.lName + '</td>'
+ '<td>' + cursor.value.fName + '</td>'
+ '<td>' + cursor.value.jTitle + '</td>'
+ '<td>' + cursor.value.company + '</td>'
+ '<td>' + cursor.value.eMail + '</td>'
+ '<td>' + cursor.value.phone + '</td>'
+ '<td>' + cursor.value.age + '</td>';
tableEntry.appendChild(tableRow);
cursor.continue();
} else {
console.log('Entries all displayed.');
}
};
};
Specifications
Specification |
---|
Indexed Database API 3.0 # ref-for-dom-idbindex-getkey① |
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 example live.)