deleteItem.js

function deleteItem(_id, table) {
  let open = indexedDB.open("books", 1);

  return new Promise(res => {
    open.onsuccess = evt => {
      let db = open.result;
      let tran = db.transaction(table, "readwrite");
      let objStore = tran.objectStore(table);
      objStore.delete(_id).onsuccess = res;
    };
  });
}