IDBIndex: getKey() method
=========================

 The **`getKey()`** method of the `IDBIndex`
 interface returns an `IDBRequest` object, and, in a separate thread,
 finds either the primary key that corresponds to the given key in this index or the
 first corresponding primary key, if `key` is set to an
 `IDBKeyRange`.

 If a primary key is found, it is set as the `result` of the request object.
 Note that this doesn't return the whole record as `IDBIndex.get` does.

**Note:** This feature is available in Web Workers

Syntax
------


```js
getKey()
getKey(key)
```

### Parameters

`key` Optional

 A key or `IDBKeyRange` that identifies a record to be retrieved. If
 this value is null or missing, the browser will use an unbound key range.


### Return value

An `IDBRequest` object on which subsequent events related to this operation are fired.

If the operation is successful, the value of the request's `result` property is the key for the first record matching the given key or key range.

### Exceptions

This method may raise a `DOMException` of one of the following types:

`TransactionInactiveError` `DOMException`

Thrown if this `IDBIndex`'s transaction is inactive.

`DataError` `DOMException`

Thrown if the key or key range provided contains an invalid key.

`InvalidStateError` `DOMException`

Thrown if the `IDBIndex` has been deleted or removed.

Examples
--------

 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` using
 `IDBObjectStore.openCursor` except that the returned records are sorted
 based on the index, not the primary key.

`myIndex.getKey('Bungle')` is then used to retrieve the primary key of the
 record with an `lName` of `Bungle`, and the result of that request
 is logged to the console when its success callback returns.

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


```js
function displayDataByIndex() {
  tableEntry.innerHTML = "";
  const transaction = db.transaction(["contactsList"], "readonly");
  const objectStore = transaction.objectStore("contactsList");

  const myIndex = objectStore.index("lName");
  const getKeyRequest = myIndex.getKey("Bungle");
  getKeyRequest.onsuccess = () => {
    console.log(getKeyRequest.result);
  };

  myIndex.openCursor().onsuccess = (event) => {
    const cursor = event.target.result;
    if (cursor) {
      const 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.");
    }
  };
}
```

Specifications
--------------

| Specification |
| --- |
| Indexed Database API 3.0 # ref-for-dom-idbindex-getkey① |

Browser compatibility
---------------------

BCD tables only load in the browser with JavaScript enabled. Enable JavaScript to view data.

See also
--------

* Using IndexedDB
* Starting transactions: `IDBDatabase`
* Using transactions: `IDBTransaction`
* Setting a range of keys: `IDBKeyRange`
* Retrieving and making changes to your data: `IDBObjectStore`
* Using cursors: `IDBCursor`
* Reference example: To-do Notifications (View the example live).