The IDBRequest
interface of the IndexedDB API provides access to results of asynchronous requests to databases and database objects using event handler attributes. Each reading and writing operation on a database is done using a request.
The request object does not initially contain any information about the result of the operation, but once information becomes available, an event is fired on the request, and the information becomes available through the properties of the IDBRequest
instance.
All asynchronous operations immediately return an IDBRequest
instance. Each request has a readyState
that is set to the 'pending'
state; this changes to 'done'
when the request is completed or fails. When the state is set to done
, every request returns aresult
and an error
, and an event is fired on the request. When the state is still pending
, any attempt to access the result
or error
raises an InvalidStateError
exception.
In plain words, all asynchronous methods return a request object. If the request has been completed successfully, the result is made available through the result
property and an event indicating success is fired at the request (IDBRequest.onsuccess
). If an error occurs while performing the operation, the exception is made available through the result
property and an error event is fired (IDBRequest.onerror
).
The interface IDBOpenDBRequest
is derived from IDBRequest
.
No methods, but inherits methods from EventTarget
.
Also inherits properties from EventTarget
.
IDBRequest.result
Read only
Returns the result of the request. If the the request failed and the result is not available, an InvalidStateError exception is thrown.
IDBRequest.error
Read only
IDBRequest.source
Read only
IDBIndex
or an IDBObjectStore
. If no source exists (such as when calling IDBFactory.open
), it returns null.IDBRequest.transaction
Read only
IDBFactory.open
unless an upgrade is needed. (You're just connecting to a database, so there is no transaction to return).IDBRequest.readyState
Read only
pending
state. The state changes to done
when the request completes successfully or when an error occurs.IDBRequest.onerror
IDBRequest.onsuccess
In the following code snippet, we open a database asynchronously and make a request; onerror
and onsuccess
functions are included to handle the success and error cases. For a full working example, see our To-do Notifications app (view example live.)
var db; // Let us open our database var DBOpenRequest = window.indexedDB.open("toDoList", 4); // these two event handlers act on the database being opened successfully, or not DBOpenRequest.onerror = function(event) { note.innerHTML += '<li>Error loading database.</li>'; }; DBOpenRequest.onsuccess = function(event) { note.innerHTML += '<li>Database initialised.</li>'; // store the result of opening the database in the db variable. db = DBOpenRequest.result; };
Specification | Status | Comment |
---|---|---|
Indexed Database API The definition of 'IDBRequest' in that specification. | Recommendation | Initial definition. |
Feature | Chrome | Edge | Firefox (Gecko) | Internet Explorer | Opera | Safari (WebKit) |
---|---|---|---|---|---|---|
Basic support | 23webkit 24 (unprefixed) | (Yes) | 10 moz 16.0 (16.0) | 10, partial | 15 | 7.1 |
Available in workers | (Yes) | ? | 37.0 (37.0) | ? | (Yes) | ? |
Feature | Android | Android Webview | Edge | Firefox Mobile (Gecko) | Firefox OS | IE Phone | Opera Mobile | Safari Mobile | Chrome for Android |
---|---|---|---|---|---|---|---|---|---|
Basic support | 4.4 | (Yes) | (Yes) | 22.0 (22.0) | 1.0.1 | 10 | 22 | 8 | (Yes) |
Available in workers | (Yes) | (Yes) | ? | 37.0 (37.0) | (Yes) | ? | (Yes) | ? | (Yes) |
IDBDatabase
IDBTransaction
IDBKeyRange
IDBObjectStore
IDBCursor
© 2005–2017 Mozilla Developer Network and individual contributors.
Licensed under the Creative Commons Attribution-ShareAlike License v2.5 or later.
https://developer.mozilla.org/en-US/docs/Web/API/IDBRequest