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IDBIndex: openCursor() method - Web APIs

Baseline Widely available

Note: This feature is available in Web Workers.

The openCursor() method of the IDBIndex interface returns an IDBRequest object, and, in a separate thread, creates a cursor over the specified key range.

The method sets the position of the cursor to the appropriate record, based on the specified direction.

If the key range is not specified or is null, then the range includes all the records.

openCursor()
openCursor(range)
openCursor(range, direction)

range Optional

A key or IDBKeyRange to use as the cursor's range. If nothing is passed, this will default to a key range that selects all the records in this object store.

direction Optional

The cursor's direction. See IDBCursor Constants for possible values.

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:

• an IDBCursorWithValue object pointing at the first record matching the given query
• null if no matching records were found.

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

TransactionInactiveError DOMException

Thrown if this IDBIndex's transaction is inactive.

TypeError

Thrown if the value for the direction parameter is invalid.

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.

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

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");

  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.");
    }
  };
}

• 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).

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