IDBKeyRange.lower

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句法
范例
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lower 只读特性在 IDBKeyRange interface returns the lower bound of the key range.

注意： 此特征可用于 Web 工作者 .

句法

var lower = myKeyRange.lower

值

The lower bound of the key range (can be any type.)

范例

The following example illustrates how you'd use a key range. Here we declare keyRangeValue = IDBKeyRange.upperBound("F", "W", true, true); — a range that includes everything between "F" and "W" but not including them — since both the upper and lower bounds have been declared as open ( true ). We open a transaction (using IDBTransaction ) and an object store, and open a Cursor with IDBObjectStore.openCursor , declaring keyRangeValue as its optional key range value.

After declaring the key range, we log its lower property value to the console, which should appear as "F".

注意 : For a more complete example allowing you to experiment with key range, have a look at our IDBKeyRange-example repo ( view the example live too )。

function displayData() {
  var keyRangeValue = IDBKeyRange.bound("F", "W", true, true);
  console.log(keyRangeValue.lower);
  var transaction = db.transaction(['fThings'], 'readonly');
  var objectStore = transaction.objectStore('fThings');
  objectStore.openCursor(keyRangeValue).onsuccess = function(event) {
    var cursor = event.target.result;
      if(cursor) {
        var listItem = document.createElement('li');
        listItem.innerHTML = '<strong>' + cursor.value.fThing + '</strong>, ' + cursor.value.fRating;
        list.appendChild(listItem);
        cursor.continue();
      } else {
        console.log('Entries all displayed.');
      }
    };
  };

规范

规范	状态	注释
索引数据库 API 2.0 The definition of 'lower' in that specification.	推荐
索引数据库 API 草案 The definition of 'lower' 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
`lower`	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： 2020 年 1 月 22 日

IndexedDB API
IDBKeyRange
特性
1. lower
2. lowerOpen
3. upper
4. upperOpen
方法
IndexedDB 相关页面

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句法

值

范例

规范

浏览器兼容性

图例

另请参阅

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