web api instance method

IDBIndex: count() method

Available in workers

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.

Syntax

count()
count(key)

Parameters

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

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 number of records that match 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 openCursor — this works the same as opening a cursor directly on an ObjectStore using 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.textContent = "";
  const transaction = db.transaction(["contactsList"], "readonly");
  const objectStore = transaction.objectStore("contactsList");

  const myIndex = objectStore.index("lName");
  const countRequest = myIndex.count();
  countRequest.onsuccess = () => {
    console.log(countRequest.result);
  };

  myIndex.openCursor().onsuccess = (event) => {
    const cursor = event.target.result;
    if (cursor) {
      const tableRow = document.createElement("tr");
      for (const cell of [
        cursor.value.id,
        cursor.value.lName,
        cursor.value.fName,
        cursor.value.jTitle,
        cursor.value.company,
        cursor.value.eMail,
        cursor.value.phone,
        cursor.value.age,
      ]) {
        const tableCell = document.createElement("td");
        tableCell.textContent = cell;
        tableRow.appendChild(tableCell);
      }
      tableEntry.appendChild(tableRow);

      cursor.continue();
    } else {
      console.log("Entries all displayed.");
    }
  };
}

Specifications

SpecificationsStandards references are available on the canonical MDN page.

Browser compatibility

Browser compatibilityCompatibility data is available on the canonical MDN page.