The IDBDatabase interface of the IndexedDB API provides a connection to a database; you can use an IDBDatabase object to open a transaction on your database then create, manipulate, and delete objects (data) in that database. The interface provides the only way to get and manage versions of the database.
Note: Everything you do in IndexedDB always happens in the context of a transaction, representing interactions with data in the database. All objects in IndexedDB — including object stores, indexes, and cursors — are tied to a particular transaction. Thus, you cannot execute commands, access data, or open anything outside of a transaction.
Immediately returns a transaction object (IDBTransaction) containing the IDBTransaction.objectStore method, which you can use to access your object store. Runs in a separate thread.
Events
Listen to these events using addEventListener() or by assigning an event listener to the oneventname property of this interface.
An event fired when a request returns an error and the event bubbles up to the connection object.
Example
In the following code snippet, we open a database asynchronously (IDBFactory), handle success and error cases, and create a new object store in the case that an upgrade is needed (IDBdatabase). For a complete working example, see our To-do Notifications app (view example live.)
// Let us open our databasevar DBOpenRequest = window.indexedDB.open("toDoList",4);// these two event handlers act on the IDBDatabase object,// when the database is opened successfully, or not
DBOpenRequest.onerror=event=>{ note.innerHTML +='<li>Error loading database.</li>';};
DBOpenRequest.onsuccess=event=>{
note.innerHTML +='<li>Database initialized.</li>';// store the result of opening the database in the db// variable. This is used a lot later on
db = DBOpenRequest.result;// Run the displayData() function to populate the task// list with all the to-do list data already in the IDBdisplayData();};// This event handles the event whereby a new version of// the database needs to be created Either one has not// been created before, or a new version number has been// submitted via the window.indexedDB.open line above
DBOpenRequest.onupgradeneeded=event=>{var db = event.target.result;
db.onerror=function(event){
note.innerHTML +='<li>Error loading database.</li>';};// Create an objectStore for this database using// IDBDatabase.createObjectStorevar objectStore = db.createObjectStore("toDoList",{keyPath:"taskTitle"});// define what data items the objectStore will contain
objectStore.createIndex("hours","hours",{unique:false});
objectStore.createIndex("minutes","minutes",{unique:false});
objectStore.createIndex("day","day",{unique:false});
objectStore.createIndex("month","month",{unique:false});
objectStore.createIndex("year","year",{unique:false});
objectStore.createIndex("notified","notified",{unique:false});
note.innerHTML +='<li>Object store created.</li>';};
This next line opens up a transaction on the Database, then opens an object store that we can then manipulate the data inside of.
var objectStore = db.transaction('toDoList','readwrite').objectStore('toDoList');