注意： 此特征可用于 Web 工作者 .

句法

var myIDBKeyRange = IDBKeyRange.lowerBound(lower);
var myIDBKeyRange = IDBKeyRange.lowerBound(lower, open);
						

参数

lower

specifies the lower bound of the new key range.

open 可选

indicates whether the lower bound excludes the endpoint value. The default is false.

返回值

IDBKeyRange : The newly created key range.

异常

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

异常	描述
DataError	The value parameter passed was not a valid key.

范例

The following example illustrates how you'd use a lower bound key range. Here we declare keyRangeValue = IDBKeyRange.lowerBound("F", false); — a range that includes the value "F" and everthing after it. 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. This means that the cursor will only retrieve the record with the key value "F" and all that come after it. If we used IDBKeyRange.lowerBound("F", true); , then the range would not include "F"; only the values after it.

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.lowerBound("F");
  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 'lowerBound()' in that specification.	推荐
索引数据库 API 草案 The definition of 'lowerBound()' 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
lowerBound	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

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