IDBIndex.openKeyCursor()

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.

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:

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.');
    }
  };
};

Specifications

Browser compatibility

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.)