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).

js
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