The lowerBound() method of the IDBKeyRange interface creates a new key range with only a lower bound. By default, it includes the lower endpoint value and is closed.

lower

Specifies the lower bound of the new key range.

open Optional

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

IDBKeyRange: The newly created key range.

DataError DOMException

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

The following example illustrates how you'd use a lower bound key range. Here we declare keyRangeValue = IDBKeyRange.lowerBound("F", false); — a range that includes the value "F" and everything after 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. This means that the cursor will only retrieve the record with the key value "F" and all that come after it. If we used IDBKeyRange.lowerBound("F", true);, then the range would not include "F"; only the values after it.

function displayData() {
  const keyRangeValue = IDBKeyRange.lowerBound("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).