IDBObjectStore.openKeyCursor() - Web APIs 编辑

The openKeyCursor() method of the IDBObjectStore interface returns an IDBRequest object whose result will be set to an IDBCursor that can be used to iterate through matching results. Used for iterating through the keys of an object store with a cursor.

To determine if the add operation has completed successfully, listen for the results’s success event.

Syntax

var request = objectStore.openKeyCursor();
var request = objectStore.openKeyCursor(query);
var request = objectStore.openKeyCursor(query, direction);

Parameters

query Optional

The key range to be queried. If a single valid key is passed, this will default to a range containing only that key. If nothing is passed, this will default to a key range that selects all the records in this object store.

direction Optional

An IDBCursorDirection telling the cursor what direction to travel. Valid values are "next", "nextunique", "prev", and "prevunique". The default is "next".

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 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:

var transaction = db.transaction("name", "readonly");
var objectStore = transaction.objectStore("name");
var request = objectStore.openKeyCursor();
request.onsuccess = function(event) {
  var cursor = event.target.result;
  if(cursor) {
    // cursor.key contains the key of the current record being iterated through
    // note that there is no cursor.value, unlike for openCursor
    // this is where you'd do something with the result
    cursor.continue();
  } else {
    // no more results
  }
};

Specifications

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 example live.)