---
title: IDBIndex.count()
slug: Web/API/IDBIndex/count
tags:
  - API
  - Database
  - IDBIndex
  - IndexedDB
  - Method
  - Reference
  - Storage
  - count
browser-compat: api.IDBIndex.count
---
{{ APIRef("IndexedDB") }}

The **`count()`** method of the {{domxref("IDBIndex")}}
interface returns an {{domxref("IDBRequest")}} object, and in a separate thread,
returns the number of records within a key range.

{{AvailableInWorkers}}

## Syntax

```js
var request = myIndex.count();
var request = myIndex.count(key);
```

### Parameters

- key {{optional_inline}}
  - : The key or key range that identifies the record to be counted.

### Return value

A {{domxref("IDBRequest")}} object on which subsequent events related to this operation
are fired.

### Exceptions

This method may raise a {{domxref("DOMException")}} of one of the following types:

- `TransactionInactiveError` {{domxref("DOMException")}}
  - : Thrown if this {{domxref("IDBIndex")}}'s transaction is inactive.
- `DataError` {{domxref("DOMException")}}
  - : Thrown if the key or key range provided contains an invalid key.
- `InvalidStateError` {{domxref("DOMException")}}
  - : Thrown if the {{domxref("IDBIndex")}} has been deleted or removed.

## Example

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 {{domxref("IDBIndex.openCursor")}} — this works the same as opening a
cursor directly on an `ObjectStore` using
{{domxref("IDBObjectStore.openCursor")}} except that the returned records are sorted
based on the index, not the primary key.

`myIndex.count()` is then used to count the number of records in the index,
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](https://github.com/mdn/indexeddb-examples/tree/master/idbindex) ([View the
example live](https://mdn.github.io/indexeddb-examples/idbindex).)

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

  var myIndex = objectStore.index('lName');
  var countRequest = myIndex.count();
  countRequest.onsuccess = function() {
    console.log(countRequest.result);
  }

  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.');
    }
  };
};
```

## Specifications

{{Specifications}}

## Browser compatibility

{{Compat}}

## See also

- [Using IndexedDB](/en-US/docs/Web/API/IndexedDB_API/Using_IndexedDB)
- Starting transactions: {{domxref("IDBDatabase")}}
- Using transactions: {{domxref("IDBTransaction")}}
- Setting a range of keys: {{domxref("IDBKeyRange")}}
- Retrieving and making changes to your data: {{domxref("IDBObjectStore")}}
- Using cursors: {{domxref("IDBCursor")}}
- Reference example: [To-do
  Notifications](https://github.com/mdn/to-do-notifications/tree/gh-pages) ([view example live](https://mdn.github.io/to-do-notifications/).)
