Recipe 5.2

Upgrading an Existing Database

This example is a contact list database implemented with IndexedDB. Contacts can be created, read, and deleted.

If you add a new object store to your database, you need to increment the database version. This triggers an upgradeneeded event where you can check the old version and determine which object store(s) need to be created.

Code

JavaScript

// todoList database is now at version 2
const request = indexedDB.open('todoList', 2);

// If the user's database is still at version 1, an `upgradeneeded` event
// is triggered so that the new object store can be added.
request.addEventListener('upgradeneeded', event => {
  const db = request.result;

  // This event is also triggered when no database exists yet, so you still need
  // to handle this case and create the `todos` object store.
  // The `oldVersion` property specifies the user's current version of the database. If the
  // database is just being created, the version is `0`.
  if (event.oldVersion < 1) {
    db.createObjectStore('todos', {
      keyPath: 'id'
    });
  }

  // If this database has not yet been upgraded to version 2, create the new object store.
  if (event.oldVersion < 2) {
    db.createObjectStore('people', {
      keyPath: 'id'
    });
  }
});

request.addEventListener('success', () => {
  // Database is ready to go
});

// Log any error that might have occurred. The error object is
// stored in the request's `error` property.
request.addEventListener('error', () => {
  console.error('Error opening database:', request.error);
});