IDBObjectStore.count() - Web APIs 编辑

The count() method of the IDBObjectStore interface returns an IDBRequest object, and, in a separate thread, returns the total number of records that match the provided key or IDBKeyRange. If no arguments are provided, it returns the total number of records in the store.

Note:

Syntax

var request = ObjectStore.count();
var request = ObjectStore.count(query);

Parameters

query Optional

A key or IDBKeyRange object that specifies a range of records you want to count.

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 count the number of records in the store using count() — when the success handler fires, we log the count value (an integer) to the console.

var transaction = db.transaction(['fThings'], 'readonly');
var objectStore = transaction.objectStore('fThings');

var countRequest = objectStore.count();
countRequest.onsuccess = function() {
  console.log(countRequest.result);
}

Specification

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.)