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.
  • 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()¬†‚ÄĒ 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 2.0
The definition of 'openKeyCursor()' in that specification.
Recommendation
Indexed Database API Draft
The definition of 'openKeyCursor()' in that specification.
Recommendation

Browser compatibility

Update compatibility data on GitHub
DesktopMobile
ChromeEdgeFirefoxInternet ExplorerOperaSafariAndroid webviewChrome for AndroidFirefox for AndroidOpera for AndroidSafari on iOSSamsung Internet
openKeyCursorChrome Full support 24
Full support 24
No support 23¬†‚ÄĒ 24
Prefixed
Prefixed Implemented with the vendor prefix: webkit
Edge Full support 12Firefox Full support 16
Full support 16
No support 10¬†‚ÄĒ 16
Prefixed
Prefixed Implemented with the vendor prefix: moz
IE Partial support 10Opera Full support 15Safari Full support 7WebView Android Full support Yes
Full support Yes
No support ?¬†‚ÄĒ ?
Prefixed
Prefixed Implemented with the vendor prefix: webkit
Chrome Android Full support 25Firefox Android Full support 22Opera Android Full support 14Safari iOS Full support 8Samsung 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.

See also