DataStoreChangeEvent

The DataStoreChangeEvent interface of the Data Store API represents the event related to a record changed in the data store, i.e. this is returned once a change is made and the change event is fired (see DataStore.onchange for the handler).

Properties

DataStoreChangeEvent.id Read only

Returns the identifier of the changed record in the data store. Must return null if the operation is cleared.

DataStoreChangeEvent.operation Read only

Returns the type of operation that represents the current change that has been made to the data store.

DataStoreChangeEvent.owner Read only

Returns the manifest URL of the application that made the change to the data store.

DataStoreChangeEvent.revisionId Read only

Returns the id of the current revision of the data store, i.e. the current change that has been made to a data record.

Example

In the following snippet we retrieve all the data stores on the device with the name "contacts", then we use DataStore.sync to create a cursor to use for syncing the app with the current "content" data store (displaying new items, etc.) This cursor is passed to the runNextTask() function that will deal with running through the updates in some way. Next, we include some code inside an onchange function so that when a change is made we return the DataStoreChangeEvent (e in this case), find out what type of operation the change is, and then take action based on this type (either adding or deleting a contact's information.)

navigator.getDataStores('contacts').then(function(stores) {
  var cursor = stores[0].sync();
  runNextTask(cursor);

  stores[0].onchange = function(e) {
    if (e.operation == 'removed') {
      // Delete the contact
      deleteContact(e.id);
    }

    if (e.operation == 'added') {
      stores[0].get(e.id).then(function(obj) {
        // Add the new contact
        loadData(obj,e.id);
      });
    }
  }
});

Operation types

The different operation types used in DataStoreChangeEvent are (see also the spec definitions):

Specifications

The discussion concerning this API's creation happened in various Mozilla mailing lists and other places. A summary of the discussion and further pointers can be found on the Mozilla Wiki. For further feedback and questions, send mail to the dev-webapi mailing list.

Browser compatibility

See also

• Using the Data Store API
• Data Store Contacts Editor example
• Data Store Contacts Viewer example changeevent version
• Data Store Contacts Viewer example cursor version