IDBCursor.direction
The direction
read-only property of the
IDBCursor
interface is a DOMString
that returns the
direction of traversal of the cursor (set using
IDBObjectStore.openCursor
for example). See the Values
section below for possible values.
Note: This feature is available in Web Workers
Value
A string (defined by the IDBCursorDirection
enum) indicating the direction in which the cursor is traversing the data.
Possible values are:
Value | Description |
---|---|
next |
This direction causes the cursor to be opened at the start of the source. |
nextunique |
This direction causes the cursor to be opened at the start of the source. For every key with duplicate values, only the first record is yielded. |
prev |
This direction causes the cursor to be opened at the end of the source. |
prevunique |
This direction causes the cursor to be opened at the end of the source.
For every key with duplicate values, only the first record is
yielded. |
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. Within each iteration we log the direction of the cursor, something like this:
prev
Note: we can't change the direction of travel of the cursor using
the direction
property, as it is read-only. We specify the direction of
travel using the 2nd argument of IDBObjectStore.openCursor
.
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 example live.)
function backwards() {
list.textContent = '';
const transaction = db.transaction(['rushAlbumList'], 'readonly');
const objectStore = transaction.objectStore('rushAlbumList');
objectStore.openCursor(null,'prev').onsuccess = function(event) {
const cursor = event.target.result;
if(cursor) {
const listItem = document.createElement('li');
listItem.innerHTML = '<strong>' + cursor.value.albumTitle + '</strong>, ' + cursor.value.year;
list.appendChild(listItem);
console.log(cursor.direction);
cursor.continue();
} else {
console.log('Entries displayed backwards.');
}
};
};
Specifications
Specification |
---|
Indexed Database API 3.0 # ref-for-dom-idbcursor-direction① |
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.)