IDBCursor: direction property
Note: This feature is available in Web Workers.
The direction
read-only property of the
IDBCursor
interface is a string that returns the
direction of traversal of the cursor (set using
IDBObjectStore.openCursor
for example). See the Value
section below for possible values.
Value
A string indicating the direction in which the cursor is traversing the data. Possible values are:
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-visited record (closest to the start) 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-visited record (closest to the end) 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.
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 the example live).
function backwards() {
list.textContent = "";
const transaction = db.transaction(["rushAlbumList"], "readonly");
const objectStore = transaction.objectStore("rushAlbumList");
objectStore.openCursor(null, "prev").onsuccess = (event) => {
const cursor = event.target.result;
if (cursor) {
const listItem = document.createElement("li");
listItem.textContent = `${cursor.value.albumTitle}, ${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 the example live).