IDBFactory.open

IDBFactory.open 方法用于打开一个数据库连接。本方法立即返回一个 IDBOpenDBRequest 对象,但打开数据库的操作是异步执行的。

连接数据库在一个单独的线程中进行,包括以下几个步骤:

  1. 指定数据库已经存在时:
    • 等待 versionchange 操作完成。
    • 如果数据库已计划删除,那等着删除完成。
  2. 如果已有数据库版本高于给定的 version,中止操作并返回类型为 VersionError 的 DOMError 。
  3. 如果已有数据库版本低于给定的 version,触发一个 versionchange 操作。
  4. 如果数据库不存在,创建指定名称的数据库,将版本号设置为给定版本,如果给定版本号,则设置为1,and no object stores.
  5. 创建数据库连接。

如果操作成功执行,将触发 success 事件 on the request object that is returned from this method, with its result attribute set to the new IDBDatabase object for the connection.

If an error occurs while the database connection is being opened, then an error event is fired on the request object returned from this method.

Syntax

For the current standard:

 IDBOpenDBRequest open (DOMString name, [EnforceRange] optional unsigned long long version);

For the experimental version with options (see below):

IDBOpenDBRequest open (DOMString name, optional IDBOpenDBOptions options);

示例

For the current standard:

var request = window.indexedDB.open("toDoList", 4);

For the experimental version with options (see below):

var request = window.indexedDB.open("toDoList", {version: 4, storage: "temporary"});

参数

name
数据库名称
version
指定数据库版本,当你想要更改数据库格式(比如增加对象存储,非增加记录),必须指定更高版本,通过 versionchange 来更改
options (version and storage) 非标准
In Gecko, since version 26, you can include an options object as a parameter of IDBFactory.open that contains the version number of the database, plus a storage value that specifies whether you want to use permanent (the default value) storage for the IndexedDB, or temporary storage (aka shared pool.) See bug 785884 for more details. This is a non-standard feature that we are looking to standardise sometime in the future.

Note: Data in temporary storage persists until the global limit for the pool is reached. The global limit calculation is relatively complex, but we are considering changing it (see  bug 968272). When the global limit is reached, then data for the least recently used origin is deleted. There's also a group limit (eTLD+1 group/domain) which is currently 20% of the global limit. All requets that would exceed the group limit are just rejected.

返回

IDBOpenDBRequest
The request object on which subsequent events related to this request are fired.

Exceptions

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

Exception 描述
TypeError The value of version is zero or a negative number or not a number.

Specifications

Specification Status Comment
Indexed Database API
The definition of 'IDBFactory' in that specification.
Candidate Recommendation  

浏览器兼容性

Feature Chrome Firefox (Gecko) Internet Explorer Opera Safari (WebKit)
Basic support 23webkit
24
10 moz
16.0 (16.0)
10, partial 15 7.1
Feature Android Firefox Mobile (Gecko) Firefox OS IE Phone Opera Mobile Safari Mobile
Basic support 4.4 22.0 (22.0) 1.0.1 10 22 Not supported

Be careful in Chrome as it still implements the old specification along with the new one. Similarly it still has the prefixed webkitIndexedDB property even if the unprefixed indexedDB is present.

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