--- title: IDBObjectStore.get() slug: Web/API/IDBObjectStore/get translation_of: Web/API/IDBObjectStore/get ---

{{ APIRef("IndexedDB") }}

{{domxref("IDBObjectStore")}} 的接口 get()方法 返回 {{domxref("IDBRequest")}} 对象，并在“单独的线程（separate thread）”中返回由指定键选择的“对象储存（object store）” 。这用于从对象储存检索特定记录。

如果成功找到值，则会创建其值的结构化克隆，并设置为“请求对象（request object）”的 result 。

{{ Note("This method produces the same result for: a) a record that doesn't exist in the database and b) a record that has an undefined value. To tell these situations apart, call the openCursor() method with the same key. That method provides a cursor if the record exists, and no cursor if it does not.") }}

{{AvailableInWorkers}}

语法

var request = objectStore.get(key);

参数

key
标识要检索的记录的键或键范围。

返回值

触发与此操作相关的后续事件的 {{domxref("IDBRequest")}} 对象。

异常

此方法可能会引发以下类型之一的 {{domxref("DOMException")}} :

Exception Description
TransactionInactiveError This {{domxref("IDBObjectStore")}}'s transaction is inactive.
DataError

The key or key range provided contains an invalid key.
InvalidStateError The {{domxref("IDBObjectStore")}} has been deleted or removed.
 

例子

在以下的代码段中，我们在数据库上打开一个“读/写 事务（read/write transaction）”，并使用 get() 从“对象储存（ object store ）”中获取一个特定的记录——一个带有“Walk dog”键的示例记录。一旦检索到这个数据对象，你就可以使用普通的JavaScript更新它，然后使用 {{domxref("IDBObjectStore.put")}} 操作将其放回数据库。有关完整的工作示例，查看我们的 To-do Notifications app (view example live.)

// Let us open our database
var DBOpenRequest = window.indexedDB.open("toDoList", 4);

DBOpenRequest.onsuccess = function(event) {
  note.innerHTML += '<li>Database initialised.</li>';

  // store the result of opening the database in the db variable.
  // This is used a lot below
  db = DBOpenRequest.result;

  // Run the getData() function to get the data from the database
  getData();
};

function getData() {
  // open a read/write db transaction, ready for retrieving the data
  var transaction = db.transaction(["toDoList"], "readwrite");

  // report on the success of the transaction completing, when everything is done
  transaction.oncomplete = function(event) {
    note.innerHTML += '<li>Transaction completed.</li>';
  };

  transaction.onerror = function(event) {
    note.innerHTML += '<li>Transaction not opened due to error: ' + transaction.error + '</li>';
  };

  // create an object store on the transaction
  var objectStore = transaction.objectStore("toDoList");

  // Make a request to get a record by key from the object store
  var objectStoreRequest = objectStore.get("Walk dog");

  objectStoreRequest.onsuccess = function(event) {
    // report the success of our request
    note.innerHTML += '<li>Request successful.</li>';

    var myRecord = objectStoreRequest.result;
  };

};

规范

Specification Status Comment
{{SpecName('IndexedDB', '#dom-idbobjectstore-get', 'get()')}} {{Spec2('IndexedDB')}}
{{SpecName("IndexedDB 2", "#dom-idbobjectstore-get", "get()")}} {{Spec2("IndexedDB 2")}}

浏览器兼容性

{{Compat("api.IDBObjectStore.get")}}

另请参阅