在此页

• 句法
• 范例
• 规范
• 浏览器兼容性
• 另请参阅
• 相关话题

count() 方法在 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.

注意： 此特征可用于 Web 工作者 .

句法

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

参数

query 可选

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

返回值

IDBRequest object on which subsequent events related to this operation are fired.

异常

此方法可能引发 DOMException of one of the following types:

异常	描述
InvalidStateError	This IDBObjectStore has been deleted.
TransactionInactiveError	This IDBObjectStore 's transaction is inactive.
DataError	The specified key or key range is invalid.

范例

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);
}
						

规范

规范	状态	注释
索引数据库 API 2.0 The definition of 'count()' in that specification.	推荐
索引数据库 API 草案 The definition of 'count()' in that specification.	推荐

浏览器兼容性

The compatibility table on this page is generated from structured data. If you'd like to contribute to the data, please check out https://github.com/mdn/browser-compat-data and send us a pull request. 更新 GitHub 上的兼容性数据

	桌面						移动
	Chrome	Edge	Firefox	Internet Explorer	Opera	Safari	Android webview	Chrome for Android	Firefox for Android	Opera for Android	Safari on iOS	Samsung Internet
count	Chrome 24 24 23 — 57 Prefixed Prefixed Implemented with the vendor prefix: webkit	Edge 12	Firefox 16 16 10 — 16 Prefixed Prefixed Implemented with the vendor prefix: moz	IE 部分支持 10	Opera 15	Safari 7	WebView Android Yes Yes ? — 57 Prefixed Prefixed Implemented with the vendor prefix: webkit	Chrome Android 25 25 25 — 57 Prefixed Prefixed Implemented with the vendor prefix: webkit	Firefox Android 22	Opera Android 14	Safari iOS 8	Samsung Internet Android 1.5 1.5 1.5 — 7.0 Prefixed Prefixed Implemented with the vendor prefix: webkit

图例

完整支持

完整支持

部分支持

部分支持

要求使用供应商前缀或不同名称。

要求使用供应商前缀或不同名称。

另请参阅

• 使用 IndexedDB
• 开始事务： IDBDatabase
• 使用事务： IDBTransaction
• 设置一系列键： IDBKeyRange
• 检索并使您的数据改变： IDBObjectStore
• 使用光标： IDBCursor
• 参考范例： 待办通知 ( 实时查看范例 )。

元数据

• 最后修改： 2020 年 1 月 22 日

相关话题

1. IndexedDB API
2. IDBObjectStore
3. 特性

   1. autoIncrement
   2. indexNames
   3. keyPath
   4. 名称
   5. transaction
4. 方法

   1. add()
   2. clear()
   3. count()
   4. createIndex()
   5. delete()
   6. deleteIndex()
   7. get()
   8. getAll()
   9. getAllKeys()
   10. getKey()
   11. index()
   12. openCursor()
   13. openKeyCursor()
   14. put()
5. IndexedDB 相关页面

   1. IDBCursor
   2. IDBCursorSync
   3. IDBCursorWithValue
   4. IDBDatabase
   5. IDBDatabaseException
   6. IDBDatabaseSync
   7. IDBEnvironment
   8. IDBEnvironmentSync
   9. IDBFactory
   10. IDBFactorySync
   11. IDBIndex
   12. IDBIndexSync
   13. IDBKeyRange
   14. IDBObjectStoreSync
   15. IDBOpenDBRequest
   16. IDBRequest
   17. IDBTransaction
   18. IDBTransactionSync
   19. IDBVersionChangeEvent
   20. IDBVersionChangeRequest