IDBObjectStore

IDBObjectStore接口描述了一个数据库中的“对象存储空间”。对象存储空间中的按照对象的键存储着不同的记录。这样的存储方式可以快速插入、查询、和有序检索。

注：为了方便理解，可以把“对象存储空间”想象成关系数据库的“表”结构，下文也会把对象存储空间称为表。

方法预览

属性

方法

add()

返回一个IDBRequest对象，并且在新线程中克隆一个值，该值存储在表中。

想知道是否成功添加数据，可以在事务的complete事件中进行监听，而不是success，因为事务在success事件之后还有可能失败。

add方法只能插入数据。如果以key参数作为某记录的关键字，并且该条记录已存在，则其所返回的请求对象会产生ConstrainError错误。

IDBRequest add (in any value, in optional any key) raises (DOMException);

参数

value

被存储的值。

key

标识某条记录的键，如果不指定，它会被设为null。

返回

IDBRequest

一个请求对象，可以在其中绑定事件。

异常

该方法会抛出DOMError类型的DOMException异常。

clear()

Creates and immediately returns an IDBRequest object, and clears this object store in a separate thread. Clearing an object store consists of removing all records from the object store and removing all records in indexes that reference the object store.

IDBRequest clear () raises (DOMException);

Returns

IDBRequest

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

Exceptions

This method may raise a DOMException with a DOMError of the following types:

count()

立即返回一个IDERequest对象，并在新线程中计算符合条件的对象的数量，该方法的参数可以是键，或键范围（key range）。在IDBRequest对象中，source属性就是IDBObjectStore对象，result属性持有计算后的数量值。如果参数非法将会抛出异常。

IDBRequest count (in optional any key) raises(DOMException);

参数

key

计算被该键或键范围（key range）所标识的记录数。

Returns

IDBRequest

一个请求对象，可绑定事件。

异常

该方法会引发如下异常：

createIndex()

创建并返回新的IDBIndex对象，该方法只能从versionchange事务模式的回调方法中被调用。

IDBIndex createIndex  (in DOMString name, in DOMString keyPath, in optional boolean unique) raises (DOMException);

Parameters

name

The name of the index to create.

keyPath

The key path for the index to use.

optionalParameters

The IDBIndexParameters object whose attributes are optional parameters to the method. It includes the following properties:

Attribute	Description
unique	If true, the index will not allow duplicate values for a single key.
multiEntry	If true, the index will add an entry in the index for each array element when the keypath resolves to an Array. If false, it will add one single entry containing the Array.

Returns

IDBIndex

The newly created index.

Exceptions

This method may raise a DOMException with a DOMError of the following types:

delete()

Immediately returns an IDBRequest object, and removes the records specified by the given key or key range from this object store, and any indexes that reference it, in a separate thread.

IDBRequest delete (in any key) raises (DOMException);

Parameters

key

The key or key range that identifies the records.

Returns

IDBRequest

A request object on which subsequent events related to this operation are fired. As per spec the result of the Object Store Deletion Operation algorithm is undefined, so it's not possible to know if some records were actually deleted by looking at the request result.

Exceptions

This method may raise a DOMException with a DOMError of the following types:

var key_val = '42';
var key = Number(key_val);
objectstore.delete(key);

deleteIndex()

Destroys the index with the specified name in the connected database. Note that this method must be called only from a VersionChange transaction mode callback. Note that this method synchronously modifies the indexNames property.

void deleteIndex (in any DOMString indexName) raises (DOMException);

Parameters

indexName

The name of the existing index to remove.

Returns

Void

Exceptions

This method may raise a DOMException with a DOMError of the following types:

get()

Immediately returns an IDBRequest object, and retrieves the requested record from the object store in a separate thread. If the operation is successful, then a success event is fired on the returned object, with its result set to the retrieved value, and transaction set to the transaction in which this object store is opened. 

IDBRequest get (in any key) raises (DOMException);

Parameters

key

The key or key range identifying the record to retrieve. In the case of a key range, the record returned is the first record associated with the first key in the range.

Returns

IDBRequest

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

Exceptions

This method may raise a DOMException with a DOMError of the following types:

index()

Opens the named index in this object store.

IDBIndex index (in DOMString name) raises (DOMException);

Parameters

name

The name of the index to open.

Returns

IDBIndex

An object for accessing the index.

Exceptions

This method may raise a DOMException with a DOMError of the following types:

openCursor()

Immediately returns an IDBRequest object, and creates a cursor over the records in this object store, in a separate thread. If there is even a single record that matches the key range, then a success event is fired on the returned object, with its result set to the IDBCursor object for the new cursor. If no records match the key range, then a success event is fired on the returned object, with its result set to null.

IDBRequest openCursor (in optional IDBKeyRange range, in optional unsigned short direction) raises(DOMException);

Parameters

range

The key range to use as the cursor's range. If this parameter is unspecified or null, then the range includes all the records in the object store.

direction

The cursor's direction.

Returns

IDBRequest

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

Exceptions

This method may raise a DOMException with a DOMError of the following types:

put()

Returns an IDBRequest object, and, in a separate thread, creates a structured clone of the value, and stores the cloned value in the object store. If the record is successfully stored, then a success event is fired on the returned request object with the result set to the key for the stored record, and transaction set to the transaction in which this object store is opened.

The put method is an update or insert method. See also the add() method.

IDBRequest put (in any value, in optional any key) raises (DOMException);

Parameters

value

The value to be stored.

key

The key to use to identify the record. If unspecified, it results to null.

Returns

IDBRequest

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

Exceptions

This method may raise a DOMException with a DOMError of the following types:

Browser compatibility