IDBCursor.direction

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范例
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direction 只读特性在 IDBCursor interface is a DOMString that returns the direction of traversal of the cursor (set using IDBObjectStore.openCursor for example). See the 值 section below for possible values.

注意： 此特征可用于 Web 工作者 .

句法

var direction = cursor.direction;

值

A string (defined by the IDBCursorDirection enum ) indicating the direction in which the cursor is traversing the data. Possible values are:

值	描述
`next`	This direction causes the cursor to be opened at the start of the source .
`nextunique`	This direction causes the cursor to be opened at the start of the source . For every key with duplicate values, only the first record is yielded.
`prev`	This direction causes the cursor to be opened at the end of the source .
`prevunique`	This direction causes the cursor to be opened at the end of the source . For every key with duplicate values, only the first record is yielded.

范例

In this simple fragment we create a transaction, retrieve an object store, then use a cursor to iterate through all the records in the object store. Within each iteration we log the direction of the cursor, something like this:

prev

注意 : we can't change the direction of travel of the cursor using the direction property, as it is read-only. We specify the direction of travel using the 2nd argument of IDBObjectStore.openCursor .

The cursor does not require us to select the data based on a key; we can just grab all of it. Also note that in each iteration of the loop, you can grab data from the current record under the cursor object using cursor.value.foo . For a complete working example, see our IDBCursor example ( 实时查看范例 )。

function backwards() {
  list.innerHTML = '';
  var transaction = db.transaction(['rushAlbumList'], 'readonly');
  var objectStore = transaction.objectStore('rushAlbumList');
  objectStore.openCursor(null,'prev').onsuccess = function(event) {
    var cursor = event.target.result;
      if(cursor) {
        var listItem = document.createElement('li');
        listItem.innerHTML = '<strong>' + cursor.value.albumTitle + '</strong>, ' + cursor.value.year;
        list.appendChild(listItem);
        console.log(cursor.direction);
        cursor.continue();
      } else {
        console.log('Entries displayed backwards.');
      }
  };
};

规范

规范	状态	注释
索引数据库 API 2.0 The definition of 'direction' in that specification.	推荐
索引数据库 API 草案 The definition of 'direction' 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
`direction`	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	Chrome Android Yes	Firefox Android 22	Opera Android 14	Safari iOS 8	Samsung Internet Android Yes

图例

完整支持
部分支持
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： Jul 31, 2020

IndexedDB API
IDBCursor
特性
1. direction
2. key
3. primaryKey
4. request
5. source
方法
IndexedDB 相关页面

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