The connection is not actually closed until all transactions created using this connection are complete. No new transactions can be created for this connection once this method is called. Methods that create transactions throw an exception if a closing operation is pending.
The method takes the name of the store as well as a parameter object that lets you define important optional properties. You can use the property to uniquely identify individual objects in the store. As the property is an identifier, it should be unique to every object, and every object should have that property.
This example shows an IDBOpenDBRequest.onupgradeneeded block that creates a new object store; it also includes onerror and onabort functions to handle non-success cases, and an onversionchange function to notify when a database structure change has occurred.