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• 句法
• 范例
• 规范
• 浏览器兼容性
• 另请参阅
• 相关话题

cmp() 方法在 IDBFactory interface compares two values as keys to determine equality and ordering for IndexedDB operations, such as storing and iterating.

注意： 此特征可用于 Web 工作者 .

注意 : Do not use this method for comparing arbitrary JavaScript values, because many JavaScript values are either not valid IndexedDB keys (booleans and objects, for example) or are treated as equivalent IndexedDB keys (for example, since IndexedDB ignores arrays with non-numeric properties and treats them as empty arrays, so any non-numeric arrays are treated as equivalent). This throws an exception if either of the values is not a valid key.

句法

var result = indexedDB.cmp(first, second);
				

参数

第一

The first key to compare.

second

The second key to compare.

返回值

An integer that indicates the result of the comparison; the table below lists the possible values and their meanings:

Returned value	描述
-1	1st key is less than the 2nd key
0	1st key is equal to the 2nd key
1	1st key is greater than the 2nd key

异常

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

属性	描述
DataError	One of the supplied keys was not a valid key.

范例

var a = 1;
var b = 2;
var result = window.indexedDB.cmp(a, b);
console.log( "Comparison results: " + result );
					

规范

规范	状态	注释
索引数据库 API 2.0 The definition of 'cmp()' in that specification.	推荐
索引数据库 API 草案 The definition of 'cmp()' 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
cmp	Chrome 24 24 23 — 24 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 ? — ? Prefixed Prefixed Implemented with the vendor prefix: webkit	Chrome Android 25	Firefox Android 22	Opera Android 14	Safari iOS 8	Samsung Internet Android 1.5

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. IDBFactory
3. 方法

   1. cmp()
   2. databases
   3. deleteDatabase()
   4. open()
4. IndexedDB 相关页面

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