IDBIndex.unique

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unique read-only property returns a boolean that states whether the index allows duplicate keys.

This is decided when the index is created, using the IDBObjectStore.createIndex method. This method takes an optional parameter, unique , which if set to true means that the index will not be able to accept duplicate entries.

注意： 此特征可用于 Web 工作者 .

句法

var isUnique = IDBIndex.unique;

值

A 布尔 :

值	Effect
`true`	The current index does not allow duplicate values for a key.
`false`	The current index allows duplicate key values.

范例

In the following example we open a transaction and an object store, then get the index lName from a simple contacts database. We then open a basic cursor on the index using IDBIndex.openCursor — this works the same as opening a cursor directly on an ObjectStore 使用 IDBObjectStore.openCursor except that the returned records are sorted based on the index, not the primary key.

The unique status of the index is logged to the console: it should be returned as false .

Finally, we iterate through each record, and insert the data into an HTML table. For a complete working example, see our IDBIndex-example demo repo ( View the example live )。

function displayDataByIndex() {
  tableEntry.innerHTML = '';
  var transaction = db.transaction(['contactsList'], 'readonly');
  var objectStore = transaction.objectStore('contactsList');
  var myIndex = objectStore.index('lName');
  console.log(myIndex.unique);
  myIndex.openCursor().onsuccess = function(event) {
    var cursor = event.target.result;
    if(cursor) {
      var tableRow = document.createElement('tr');
      tableRow.innerHTML =   '<td>' + cursor.value.id + '</td>'
                           + '<td>' + cursor.value.lName + '</td>'
                           + '<td>' + cursor.value.fName + '</td>'
                           + '<td>' + cursor.value.jTitle + '</td>'
                           + '<td>' + cursor.value.company + '</td>'
                           + '<td>' + cursor.value.eMail + '</td>'
                           + '<td>' + cursor.value.phone + '</td>'
                           + '<td>' + cursor.value.age + '</td>';
      tableEntry.appendChild(tableRow);
      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 'unique' in that specification.	推荐
索引数据库 API 草案 The definition of 'unique' 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
`unique`	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
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
IDBIndex
特性
1. isAutoLocale
2. keyPath
3. locale
4. multiEntry
5. 名称
6. objectStore
7. unique
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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