The upperBound() method of the IDBKeyRange interface creates a new upper-bound key range. By default, it includes the upper endpoint value and is closed.

upper

Specifies the upper bound of the new key range.

open Optional

Indicates whether the upper bound excludes the endpoint value. The default is false.

IDBKeyRange: The newly created key range.

DataError DOMException

Thrown if the key associated with the upper parameter is not a valid key.

The following example illustrates how you'd use an upper bound key range. Here we declare keyRangeValue = IDBKeyRange.upperBound("F"); — a range that includes the value "F" and everything before it. We open a transaction (using IDBTransaction) and an object store, and open a Cursor with IDBObjectStore.openCursor, declaring keyRangeValue as its optional key range value.

If we used IDBKeyRange.upperBound("F", true);, then the range excludes "F"; and instead only includes the values before it.

function displayData() {
  const keyRangeValue = IDBKeyRange.upperBound("F");

  const transaction = db.transaction(["fThings"], "readonly");
  const objectStore = transaction.objectStore("fThings");

  objectStore.openCursor(keyRangeValue).onsuccess = (event) => {
    const cursor = event.target.result;
    if (cursor) {
      const listItem = document.createElement("li");
      listItem.textContent = `${cursor.value.fThing}, ${cursor.value.fRating}`;
      list.appendChild(listItem);

      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).