index.js

const Items = db.transaction(["items"], "readwrite").objectStore("items");
Items.get(3)
  .onsuccess = function(event) {
    const row = event.target.result;
    row.name = "商品3の名前を変更";
    Items
      .put(row)
      .onsuccess = function(event) {
        console.log("更新しました");
      }
  }