IDBIndex.count()

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

Note: This feature is available in Web Workers

Syntax

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

Parameters

key Optional: The key or key range that identifies the record to be counted.

Return value

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

Exceptions

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

Exception	Description
`TransactionInactiveError`	This `IDBIndex`'s transaction is inactive.
`DataError`	The key or key range provided contains an invalid key.
`InvalidStateError`	The `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 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.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 (View the example live.)

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

Specification
Indexed Database API 3.0 (Indexed DB 3.0) # ref-for-dom-idbindex-count①

Browser compatibility

	Desktop						Mobile
	Chrome	Edge	Firefox	Internet Explorer	Opera	Safari	WebView Android	Chrome Android	Firefox for Android	Opera Android	Safari on IOS	Samsung Internet
`count`	23	12	10	10	15	7	≤37	25	22	14	8	1.5