Web/API/IDBindex/openKeyCursor-2

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.
A success event is always fired on the result object.
- If at least one key matches the key range, then the result property of the event is set to the new IDBCursor object; the key property of the cursor object is set to the found key and the primaryKey property is set to the the corresponding primary key of the found record.
- If no keys match the key range, then then the result property of the event is set to null.

Note: Cursors returned by openKeyCursor() do not make the referenced value available as IDBIndex.openCursor does. This makes obtaining a list of keys much more efficient.

Note: This feature is available in Web Workers.

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:

Exception	Description
`TransactionInactiveError`	This `IDBIndex`'s transaction is inactive.
`TypeError`	The value for the direction parameter is invalid.
`DataError`	The key or key range provided contains an invalid key.
`InvalidStateError`	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 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.');    
    }
  };
};

Specification

Specification	Status	Comment
Indexed Database API 2.0The definition of 'openKeyCursor()' in that specification.	Recommendation
Indexed Database API DraftThe definition of 'openKeyCursor()' in that specification.	Recommendation

Browser compatibility

Update compatibility data on GitHub

	Desktop						Mobile
	Chrome	Edge	Firefox	Internet Explorer	Opera	Safari	Android webview	Chrome for Android	Firefox for Android	Opera for Android	Safari on iOS	Samsung Internet
`openKeyCursor`	Chrome Full support 24 Full support 24 No support 23 — 24 Prefixed' Prefixed' Implemented with the vendor prefix: webkit	Edge Full support 12	Firefox Full support 16 Full support 16 No support 10 — 16 Prefixed' Prefixed' Implemented with the vendor prefix: moz	IE Partial support 10	Opera Full support 15	Safari Full support 7	WebView Android Full support Yes Full support Yes No support ? — ? Prefixed' Prefixed' Implemented with the vendor prefix: webkit	Chrome Android Full support 25	Firefox Android Full support 22	Opera Android Full support 14	Safari iOS Full support 8	Samsung Internet Android Full support 1.5

Legend

Full support: Full support
Partial support: Partial support
Requires a vendor prefix or different name for use.': Requires a vendor prefix or different name for use.